Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.24.3 (collagenase)
18,340 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

AVP dependent adenylate cyclase activity was measured in single pieces of 8 different tubular segments isolated from collagenase treated rabbit kidneys. High responses were observed in all the tested portions of the collecting tubule, that is its cortical branched part (BCT), its cortical straight part (CCT) and its outer medullary part (MCT). Dose response curves indicated in CCT: 2 fold threshold stimulation at 10(-11) M AVP, 27 fold stimulation at 10(-6) M AVP, half maximal stimulation at about 10(-9) M AVP. Both the medullary (MAL) and, to a lesser extent, the cortical (CAL) portions of the thick ascending limb were also observed to contain AVP sensitive adenylate cyclase (for MAL: 2 fold threshold stimulation at 10(-9) M AVP, 9 fold stimulation at 10(-7) M AVP, half maximal stimulation at 5 X 10(-9) M AVP). In contrast, nearly no responsiveness to AVP was observed in the proximal convoluted tubule, in the thin descending limb of the loop and in the distal convoluted tubule (DCT). The limited response obtained in DCT (which is a structure generally considered as a target site for AVP) as well as the clearcut effect elicited by AVP in MAL (the functioning of which is not known to be controlled by ADH) were expected observations; their possible physiological implications will be discussed.
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PMID:Vasopressin dependent adenylate cyclase in single segments of rabbit kidney tubule. 17 59

Rabbit distal convoluted tubules (DCT) microdissected from collagenase-treated kidneys were observed to contain up to four portions of a different appearance under stereomicroscopic examination: (1) a DCTa portion (generally very short), located right after the macula densa (MD) and resembling the portion of the limb (CAL) located before the MD; (2) a constant, "bright" portion, DCTb; (3) a constant, "granular" DCTg portion which, in most DCT, is connected to a portion of the collecting tubule of a similar "granular" appearance (CCTg); (4) many DCT having contacts with the kidney capsule in the superficial cortex were observed to contain an additional portion of a "light" appearance, DCTl, resembling the portion of the collecting tubule (CCTl) to which these superficial DCT are always branched. The hormone-dependent adenylate cyclase (AC) contained in these different portions was investigated by sectioning microdissected distal structures into successive samples according to the above-mentioned criteria, and by measuring with the help of a previously described micromethod, the enzyme activity contained in each single sample under one of the following conditions: control, parathyroid hormone. (PTH l U/ml), vasopressin, (AVP 10(-6)M), isoproterenol (10(-6)M), fluoride (5 X 10(-3)M). Highly significant and reproducible AC stimulations by these hormones were obtained for the following portions, respectively: DCTa, DCTg and CCTg with PTH; DCTl and CCTl with AVP; DCTg, CCTg and CCTl with isoproterenol. From these data, it is concluded that (a) the distal convoluted tubule can no longer be regarded as a single well-defined functional structure; (b) DCTa is actually a short CAL portion extending beyond MD, (c) DCTg and CCTg are two portions of a same functional segment; (d) similarly, DCTl belongs to the functional segment mainly constituted by CCTl; and, finally, (e) DCTb is the only functional segment which is entirely located in the distal convoluted tubule, i.e., included between the macula densa and the first branching with another tubule.
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PMID:Functional segmentation of the rabbit distal tubule by microdetermination of hormone-dependent adenylate cyclase activity. 94 Feb 69

A microassay was developed to measure the binding of the labelled monoiodinated analogue [1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid), 2-O-methyltyrosine, 4-threonine, 8-ornithine, 9-125I-tyrosylamide]vasotocin [125I-d(CH2)5[Tyr (Me)2, Thr4, Tyr-NH(2)9]OVT] to isolated nephron segments microdissected from collagenase-treated rat kidneys. When determined using 1.7 nM labelled ligand at 4 degrees C, specific binding sites (expressed at 10(-18) mol 125I-d(CH2)5[Tyr (Me)2, Thr4, Tyr-NH(2)9]OVT bound/mm tubule length) were found in medullary thick ascending limbs (MTAL), 1.67 +/- 0.49; cortical thick ascending limbs, 2.20 +/- 0.80; cortical collecting ducts, 2.39 +/- 0.86; outer medullary collecting ducts (OMCD), 2.54 +/- 0.53 and inner medullary collecting ducts, 5.33 +/- 0.40, whereas no specific binding could be detected in glomeruli and proximal tubules. Specific 125I-d(CH2)5[Tyr (Me)2, Thr4, Tyr-NH(2)9]OVT binding to OMCD was saturable with incubation time and reversible after elimination of free labelled ligand (the association and dissociation rate constants at 4 degrees C were 1.06 x 10(7) M-1 min-1 and 1.95 x 10(-2) min-1 respectively). The stereospecificity of MTAL and OMCD binding sites was assessed in competitive experiments revealing the following recognition pattern for a series of eight vasopressin analogues:dDAVP greater than AVP greater than d(CH2)5-[Tyr (Me)2, Thr4, Tyr-NH(2)9]OVT = AVT = OT greater than d(CH2)5[Tyr(Me)2]AVP = [Thr4, Gly7]OT greater than [Phe2, Orn8]VT, whereas pharmacological concentrations of insulin and glucagon did not impair radioligand binding. These results indicate that the detected labelled binding sites might correspond mainly to physiological V2 vasopressin receptors.
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PMID:Receptors for neurohypophyseal hormones along the rat nephron: 125I-labelled d(CH2)5[Tyr(Me)2, Thr4, Orn8, Tyr-NH(2)9] vasotocin binding in microdissected tubules. 183 Mar 90

A microradioimmunoassay has been developed in order to measure the changes in cGMP cell content induced in vitro by atrial natriuretic peptides (ANP) in either glomeruli or defined portions of tubules microdissected from collagenase treated rat and rabbit kidneys. When tested at 0.1 microM or 1 microM, all ANP analogues used produced in rat glomeruli a 20-25 fold increase in cGMP accumulation compared to basal values. Threshold responses were obtained with about 1 nM ANP and apparent Ka values ranged between 5 and 50 nM. Atriopeptin III led to similar results in glomeruli isolated from rabbit. Under the same experimental conditions, no cGMP could be detected in any ANP-treated nephron segment from the rat kidney (namely, from the proximal convoluted tubule up to the outer medullary collecting tubule) nor in cortical collecting tubules isolated from the rabbit kidney. Moreover, ANP did not alter the forskolin-induced increase in cAMP content in glomeruli or collecting tubules, nor the AVP-induced increase in cAMP content in collecting tubules. Our data confirm the marked effect of ANP on cGMP generation by isolated glomeruli from rat and rabbit; however, they are not compatible with a direct action of ANP stimulating cGMP generation in tubules or inhibiting vasopressin-induced cAMP generation in collecting tubules.
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PMID:Atrial natriuretic peptide effects on cGMP and cAMP contents in microdissected glomeruli and segments of the rat and rabbit nephrons. 243 41

The production of prostaglandins by rat renal tubular cells and by rat vascular smooth muscle cells (VSMC) in response to vasoactive hormones was examined. A superfusion technique was used to stimulate collagenase-dispersed renal cortical or medullary tubular cells and trypsinized rat aortic smooth muscle cells with vasoactive hormones and ANF. All cell types responded promptly to the stimuli in a dose-dependent manner. Renal tubular cells produced mainly PGE2, less PGF2 alpha and no 6-keto-PGF1 alpha, while VSMC produced exclusively 6-keto-PGF1 alpha. This production of PG was strictly dependent on the presence of extracellular Ca2+ and was not inhibited by antagonists of voltage-dependent Ca2+-channels. Angiotensin II (Ang II) was active on cortical tubular cells and VSMC. Sar1-Ala8-angiotensin II blocked this action. Arginine-vasopressin (AVP acted on medullary tubular cells and VSMC and its effect was inhibited by selective V1-antagonists. The V2-agonist dDAVP had no effect on PG production. A clear distinction between V1-receptor mediated PG release and V2-receptor mediated cAMP extrusion was observed in medullary tubular cells. Bradykinin was a weak agonist on medullary tubular cell. The synthetic (1-24) atrial natriuretic peptide did not prevent 6-keto-PGF1 alpha release induced by Ang II or AVP in VSMC nor the PGE2 release in cortical tubular cells induced by Ang II.
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PMID:The regulation of prostaglandins by vasoactive hormones in renal tubular and vascular smooth muscle cells. 312 55

The relationship between vasopressin (VP) receptor levels in the anterior pituitary and VP-stimulated ACTH release in vitro was studied in rats subjected to various chronic stress paradigms. The stress models used were water deprivation for 60 h and administration of 2% NaCl in the drinking water (both of which are associated with decreased pituitary ACTH responsiveness), and repeated i.p. hypertonic saline injections or repeated daily immobilization for 14 days (associated with increased ACTH responsiveness to novel stimuli). VP receptors were measured by binding of [3H]arginine-VP to anterior pituitary membrane-rich fractions, and ACTH responses to VP in collagenase dispersed anterior pituitary cells. In control rats, binding of [3H]AVP was saturable and high affinity, with a Kd of 0.45 +/- 0.05 nM and a Bmax of 138.8 +/- 8.1 fmol/mg. In pituitary membranes from stressed rats, binding affinity was unchanged, but Bmax changed according to the type of stress. While VP binding was markedly reduced after water deprivation and 2% saline (25% and 49%, respectively), it was significantly increased after repeated i.p. hypertonic saline injections and repeated immobilization (126% and 154% of controls, respectively). The changes in VP binding were associated to parallel changes in maximum VP-stimulated ACTH production in vitro, with a 34% decrease in water deprived rats and a 25% increase in hypertonic saline injected rats. The potentiating effect of VP on corticotropin releasing hormone-stimulated ACTH was also reduced in cells from water-restricted rats, and increased in cells from rats given repeated injections of hypertonic saline. The data show a direct relationship between changes in corticotroph responsiveness and changes in pituitary VP receptors during chronic stress, suggesting that pituitary VP receptor regulation is involved in the adaptation of the HPA axis during chronic stress.
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PMID:Regulation of pituitary vasopressin receptors during chronic stress: relationship to corticotroph responsiveness. 761 75

Adenylate cyclase sensitivity to neurohypophyseal hormones was investigated in isolated glomeruli and in nephron segments microdissected from collagenase-treated kidneys of Rana ridibunda. Vasotocin treatment increased adenylate cyclase activity in glomeruli and in collecting ducts and did not modify it in proximal convoluted tubules and in early and late distal tubules. In glomeruli, the hormonal stimulation resulted mainly in a decrease in the Km value for adenylate cyclase, which means a higher affinity for substrate (ATP) to the enzyme, whereas the response to forskolin was accounted for by increases both in affinity for substrate and in maximal adenylate cyclase velocity. The homologous neurohypophyseal hormones stimulated frog glomerular adenylate cyclase with the following rank order of affinities: hydrin 1 > or = AVT = AVP > or = hydrin 2 > OT > or = mesotocin > isotocin; structural analogs dDAVP, VDAVP, dVDAVP, and [Phe2,Orn8]VT had weak agonistic properties, [Thr4,Gly7]OT was inactive, and the antagonists OVTA, d(CH2)5Tyr(Et)2VAVP, and des-Gly9-d(CH2)5Tyr(Et)2VAVP inhibited hormone-induced enzyme activation with similar apparent inhibition constants. The vasotocin receptors triggering adenylate cyclase stimulation in frog glomeruli differ pharmacologically from V2 vasopressin receptors of mammalian kidneys and may also differ from V2-like vasotocin receptors of amphibian skin and urinary bladder.
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PMID:Vasotocin-sensitive adenylate cyclase in frog glomeruli. 778 59

Vasotocin receptors were investigated in glomeruli and nephron segments microdissected from collagenase-treated kidneys of Rana ridibunda, using [d(CH2)5Tyr(Me)2,Thr4,Orn8,125I-Tyr-NH2(9)]vasotocin (125I-OVTA) as a radioligand. Specific 125I-OVTA binding sites were found only in glomeruli and not in all tubule segments tested. Glomerular receptors exhibited the following stereospecificity for recognition of vasotocin analogues: Tyr-NH2(9)-LA-V1a > 125I-OVTA > arginine vasotocin (AVT) > or = [d(CH2)5Tyr-(Me)2]AVP > OVTA > or = [Phe2,Orn8]VT > oxytocin (OT) > or = [d(CH2)5-Sar7]AVP > desGly9[d(CH2)5Tyr(Et)2]VAVP > or = [d(CH2)5Tyr(Et)2]VAVP > AVP > [1-desamino-8-D-arginine]vasopressin (DDAVP) > [Thr4,Gly7]OT. In addition, vasotocin enhanced [3H]inositol phosphate production in sieved glomeruli labeled with myo-[3H]inositol; the rank order of structural vasotocin analogues for stimulation of phosphoinositidase C was [Phe2,Orn8]VT > AVT > OT > AVP > DDAVP, whereas [Thr4,Gly7]OT was almost inactive, and the rank order of antagonists for inhibition of hormone-induced enzyme activation was Tyr-NH2(9)-LA-V1a > [d(CH2)5Tyr(Me)2]AVP = OVTA > [d(CH2)5Sar7]AVP > [d(CH2)5Tyr(Et)2]VAVP > or = desGly9[d(CH2)5Tyr(Et)2]VAVP. Results indicate that the 125I-OVTA-labeled binding sites detected in frog glomeruli reveal the pharmacological properties of mammalian V1b-pituitary vasopressin receptors and might be physiological vasotocin receptors involved in phosphoinositidase C stimulation.
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PMID:Frog glomerular vasotocin receptors resemble mammalian V1b receptors. 797 46

Liver regeneration following partial hepatectomy is significantly impaired in rats with hereditary vasopressin (AVP) deficiency. This suggested that AVP might have a direct effect on cultured rat hepatocytes. Hepatocytes from male Sprague-Dawley rats were isolated using a two-step collagenase perfusion technique and plated at a density of 10(5)/16-mm Primaria plate. After a suitable attachment period, hepatocytes were incubated with minimal essential media, AVP, AVP plus a specific AVP antagonist, or oxytocin. Hepatocyte proliferation was measured by [3H]thymidine incorporation ([3H]Thy) into hepatocyte DNA. AVP (10 nM) increased [3H]Thy significantly (and this effect was blocked by an AVP-specific antagonist (50 nM). Oxytocin had no effect on hepatocyte DNA synthesis. To further investigate the influence of AVP on hepatocyte proliferation, the effect of AVP on transforming growth factor-alpha (TGF-alpha)-stimulated hepatocyte proliferation was also studied. This combination was chosen based on the ability of AVP to inhibit the biologic effects of EGF (a TGF-alpha analog). There was significant attenuation of TGF-alpha (50 nM)-stimulated [3H]Thy in the presence of AVP (10 nM). In summary: (1) AVP stimulates proliferation of cultured rat hepatocytes. (2) The effect of AVP can be significantly abolished by a specific AVP antagonist. (3) The proliferative response of AVP is specific. (4) AVP significantly attenuates TGF-alpha-stimulated hepatocyte hepatic DNA synthesis. Further studies should elucidate the mechanisms for the effects of AVP on hepatic proliferation alone or in combination with other factors.
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PMID:Vasopressin stimulates DNA synthesis in cultured rat hepatocytes. 799 50

The multifactorial control of ACTH is well established. We wished to establish and characterize an in-vitro perifusion system, using equine anterior pituitary cells and physiological concentrations of secretagogues, to investigate factors which affect the dynamics of ACTH secretion. Anterior pituitary tissue was divided for dispersion into cells with collagenase, trypsin or dispase, or by mechanical dispersion. After dispersal followed by 18-h incubation, cells were perifused and the ACTH response to 10-min pulses of arginine vasopressin (AVP; 100 nmol/l), corticotrophin-releasing hormone (CRH; 0.01 nmol/l), and AVP (100 nmol/l) plus CRH (0.01 nmol/l) determined. ACTH responses to these secretagogues were lower (P < 0.05) in cells prepared using the enzymes dispase and trypsin than with the enzyme collagenase. Cells prepared by mechanical methods were not responsive. Collagenase-prepared cells were used in subsequent experiments. In dose-response studies (10-min pulse length), a steep CRH-ACTH dose-response curve was obtained with the minimum effective concentration of CRH between 0.001 and 0.01 nmol/l, and a maximum effective concentration of 1.0 nmol/l. A less steep AVP-ACTH dose-response curve was obtained with a minimum effective concentration of AVP between 0.5 and 5 nmol/l, and no plateau in response up to 5000 nmol AVP/l. Increasing the incubation time between cell preparation and stimulation with AVP from 18 h to 90 h significantly (P < 0.01) increased the ACTH response. Repeated stimulation by AVP (100 nmol/l) or CRH (0.01 nmol/l) (5-min pulses every 30 min for 23 pulses) produced ACTH responses which decreased in an approximately exponential curve with time. When AVP and CRH were given at physiological concentrations, pulse lengths and pulse frequency, the ACTH response to repeated 1-min pulses of AVP, measured as height above basal secretion, was potentiated by the addition of CRH (1, 2.5, 5, 10 and 20 pmol/l) as a constant perifusion at all AVP concentrations tested (1 nmol AVP/l, P < 0.02; 10 nmol AVP/l, P < 0.0005; 25 nmol AVP/l, P < 0.0005). During the 1-min AVP pulse, the AVP concentration at the level of the cells was 30% of the expected concentration. Potentiation was increased both by increasing AVP concentration (P < 0.00005) and by increasing CRH concentration (P < 0.00005) up to 5 pmol CRH/l. The ACTH height response to repeated AVP stimulation significantly (P = 0.034) decreased with time, independent of CRH and AVP concentration. There was a significant (P = 0.014) decrease in ACTH response to CRH infusion with time, independent of CRH concentration.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Factors affecting ACTH release from perifused equine anterior pituitary cells. 839 18


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