Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. A-V differences and milk concentrations of respiratory gases, pH, HCO3 and H2CO3 have been measured in lactating goats and cows. 2. The pH and [HCO3 minus] of milk were significantly lower than those of plasma while milk PCO2 was virtually identical to that of mammary venous blood. [H2CO3+ dissolved CO2] was similar in milk and blood. 3. 14-C (from injected [14-C]HCO3 minus was found to cross the mammary epithelium in both directions. 14-C also passed across the duct epithelium and since this epithelium has previously been shown to be impermeable to ions it is argued that 14-C crossed in an unionized form, i.e. as CO2 and/or H2CO3. 4. Hourly milking with the aid of oxytocin raised milk pH, [HCO3 minus], [H2CO3], [Na] and E1Cl], and lowered [K], [lactose] and [phosphate]. These effects are discussed in relation to the hypothesis proposed previously for the action of oxytocin on milk composition. 5. A scheme for the distribution and movements of CO2, H2CO3 and HCO3 minus between extracellular fluid and milk is suggested, and discussed in relation to Cl minus transport.
 ...
PMID:The distribution and movements of carbon dioxide, carbonic acid and bicarbonate between blood and milk in the goat. 23 18

1. The time course of appearance of radioactivity in milk was studied following close-arterial infusion of labelled phosphate, Ca or leucine into the mammary artery of lactating goats. Maximum activities were reached at 1.5 hr in all milk fractions including inorganic soluble phosphate, inorganic colloidal phosphate, casein P, soluble Ca, protein-associated Ca and casein. 2. At 0.5 hr, labelling of the soluble and colloidal phosphate fractions was significantly higher than that of the casein P. 3. Recovery of 32P or 47Ca 3 or more hours after infusion into the cistern of the mammary glands was 98% or greater, indicating that the mammary epithelium is virtually impermeable to [32P]phosphate and 47Ca in the milk to blood direction. 4. Ca and P failed to enter milk in excess of the normal secretion rate when the milk was diluted with isosmotic sucrose given by intraductal injection. 5. These data suggest that milk Ca and phosphate in their various forms are secreted, like protein and lactose, by exocytosis of Golgi vesicles. Unless a paracellular pathway is present, as in oxytocin-treated animals, the milk concentrations are maintained by virtue of the impermeability of the mammary epithelium to these substances.
 ...
PMID:The secretion of calcium and phosphorus into milk. 46 1

1. In conscious lactating goats a significant correlation was found between blood-milk potential difference (p.d.) and milk [lactose] such that in goats with a lower milk [lactose], milk was more negative with respect to blood.2. When mannose was substituted for glucose in the substrate mixture of isolated perfused goat mammary glands, milk yield and milk [lactose] fell while milk [Na] and [K] increased; in parallel experiments the blood-milk p.d. changed such that milk became more negative with respect to blood. These changes were reversed following the addition of glucose.3. When milk was made hypertonic by the addition of hyperosmotic sucrose or lactose solutions, water entered milk osmotically and milk became electrically less negative or even positive with respect to blood in goats, cows and guinea-pigs.4. No effect on p.d. was apparent following the addition of isosmotic sucrose to milk in goats.5. When milk was held in the teat of goats by a pneumatic cuff around the base of the teat, no effect on p.d. was apparent when hyperosmotic sucrose was introduced into this teat pouch.6. It is suggested that waterflow-induced potentials (the streaming potential and the transport number effect) can be induced across the mammary epithelium.7. In goats exogenous oxytocin lowered milk [lactose] and blood-milk p.d. became less negative with respect to blood.8. In non-lactating and mastitic glands of goats the blood-milk p.d. was within 0.5-2.5 mV of zero.9. The effects of oxytocin, and the low p.d. in non-lactating and mastitic glands, are compatible with the view that in such circumstances there is a paracellular pathway across the mammary epithelium which partially short-circuits the two sides.10. It is suggested that, with water being drawn osmotically into milk to dilute newly formed lactose, waterflow-induced potentials may be responsible for establishing the normal p.d. across the apical membrane of the secretary cell, thereby keeping milk [K] and [Na] lower than in intracellular fluid.
 ...
PMID:Mechanism of milk secretion: milk composition in relation to potential difference across the mammary epithelium. 90 3

1. The time course of changes in specific activities of citrate, lactose and fatty acids in milk during frequent milking, following the I.V. administration of labelled glucose, acetate and chylomicrons in goats has been studied. Peak specific activities of lactose and citrate in milk were reached at 2-3 hr, while peak specific activites of fatty acids were reached at 5-7 hr. 2. Following short I.A. infusions of 24Na, 36Cl, and 42K, peak specific activities in milk were reached in 1 hr or less. 3. The mammary epithelium of lactating goats was found to be virtually impermeable to labelled citrate in both directions. 4. Labelled citrate had an apparent volume of distribution in lactating guinea-pigs mammary slices in vitro similar to that of extracellular space markers. 5. Treatment of goats with large doses of oxytocin markedly increased the permeability of the secretory epithelium to labelled citrate. 6. In the goat mammary gland, citrate, protein and calcium failed to enter milk which had been diluted with isosmotic lactose by intraductal injection, whereas Na, K and Cl did enter, thus tending to restore the concentrations of these ions to normal. 7. It is suggested that citrate, which is formed within the sucretory cell, enters milk not by passage across the apical cell membrane but, in common with lactose and milk protein, by exocytosis of Golgi vesicles. It appears that citrate is held at high concentrations in milk by virtue of the impermeability of the mammary epithelium to the forms in which it occurs in milk.
 ...
PMID:The secretion of citrate into milk. 97 74

Milk samples were from stomachs of 27 nursing cottontail rabbits (Sylvilagus floridanus) within 5 min after cessation of nursing. Four milk samples were directly from mammary glands by hand milking aided by tranquilizer and oxytocin. Means and standard errors for 27 stomach samples for total solids, fat, protein, lactose, and ash were 33.6 +/- .8%, 13.9 +/- 1.7%, 14.6 +/- .5%, 2.22 +/- .05%, and 2.06 +/- .07%. Those values of 4 samples directly from the gland were 35.2 +/- .4%, 14.4 +/- .4%, 15.8 +/- .6%, 2.67 +/- .26%, and 2.07 +/- .06%. Fatty acid compositions were similar for the groups, except linoleic acid was 30.0% of fatty acids from stomach milk and 24.7% in milk obtained directly. Differences between sampling methods in palmitoleate, stearate, and oleate may have been from differences in season of sampling. Minerals were more concentrated in milk obtained directly, except potassium. Differences between milks of domesticated and cottontail rabbits are discussed.
 ...
PMID:Composition of cottontail rabbit milk from stomachs of young and directly from gland. 118 5

The effects of prolactin or oxytocin on milk secretion and the permeability of the mammary epithelium have been investigated in rabbits. 2. Milk yield was increased by prolactin treatment in late (25-28 days) but not in established (11-14 days) lactation. 3. Prolactin treatment increased milk [lactose] and [K] and decreased [Na] and [Cl] in late lactation, and thus reversed the normal changes in late lactation, but had no significant effect in established lactation. 4. [14C]sucrose movements from blood to milk were significantly decreased to levels characteristic of established lactation, following prolactin treatment in late lactation. No significant effect was evident with treatment in established lactation. Na and Cl movements showed similar trends. 5. It is suggested that prolactin in some way affects paracellular movements of ions and small molecules like lactose across the mammary epithelium, and that this mechanism is responsible for the changes in the composition of the aqueous phase of milk. 6. Immediately following a single dose of 100 m-u. oxytocin no significant effects on milk composition were evident but after 1 u. milk [Na] and [cl] were significantly increased. 7. Twenty-four hr after 1 u. oxytocin, milk [Na] and [cl] were decreased while [K], [lactose], [fat] and [protein] were increased. 8. During an I.V. infusion of oxytocin milk [Na] and [Cl] increased while [K] and [lactose] decreased. The passage of [(14)C]sucrose, 24Na and (36)Cl from blood to milk also increased. 9. These effects of oxytocin are discussed in relation to the permeability of the mammary epithelium and the pathways for ion movements, and to other studies on milk composition in the rabbit involving the administration of oxytocin to aid in the evacuation of milk.
 ...
PMID:The effects of prolactin and oxytocin on milk secretion and on the permeability of the mammary epithelium in the rabbit. 121 26

Supraphysiological doses of oxytocin were used to investigate the association among milk composition, secretion rates, and cell electrolyte concentrations. Groups of 8 Holstein cows were injected i.v. with 1, 10, 100, or 1000 IU oxytocin after a normal milking. Milk yield over the following 12-h period declined 5.5, 8.1, 17.0, and 43.7% respectively. Milk Na increased in proportion to oxytocin dose. Yield and concentration of lactose and protein declined with increasing oxytocin doses, but milk fat yield remained unchanged. To determine whether the decreased milk lactose secretion was caused by a decline in synthesis or leakage into blood plasma and subsequent renal clearance, milk and urine were collected for 24-h periods before and after 100 IU oxytocin. Urinary lactose accounted for 2.7 +/- 3.19 and 12.9 +/- 8.9% of the total collected on the days before and after oxytocin. This increase (46.7 g/d) was only one-fifth of the 25% decline in total lactose recovery, suggesting that reduced mammary lactose synthesis is primarily responsible for lower milk yield. Measurement of Na and K in biopsied mammary tissue suggests that a high Na:K ratio in milk will increase that ratio in secretory cells, which may be part of the mechanism for lower milk yield under circumstances that increase permeability of mammary tight junctions.
 ...
PMID:Milk synthesis and secretion rates in cows with milk composition changed by oxytocin. 234 8

The ability of lipoprotein lipase to move across the mammary epithelium by a paracellular route was investigated. Five goats were milked hourly to activate the paracellular pathway. Three goats responded to hourly milking with a fivefold increase in milk lipoprotein lipase activity as compared with nonresponding goats. Massage of the mammary gland was necessary in the two nonresponding goats too cause increased lipoprotein lipase activity in milk. Oxytocin treatment during hourly milking also increased enzyme activity in milk from a nonresponding goat. Activation of the paracellular pathway by hourly milking increased milk sodium and protein and decreased potassium and lactose concentrations. After a 12-h milking interval, lipoprotein lipase activity was distributed primarily in the serum (48%) and cream (40%) fractions and, to a lesser extent, in the casein (12%) fraction. Hourly milking increased enzyme activity distributed in the serum fraction (62%), whereas enzyme activity associated with the cream (32%) and casein (6%) fractions decreased. Possible mechanisms for the origin of lipoprotein lipase in milk are discussed.
 ...
PMID:Paracellular leakage of lipoprotein lipase across the mammary epithelium of the goat. 274 24

The lipid content of milk expressed from rats decreased from 15.8% wt/vol within 1 h of the removal of the pups to 4.2% in samples obtained 12 h after the removal of the pups. The protein and lactose concentrations were unchanged. Analysis of gland homogenates showed that lactose and total lipid accumulated throughout the 12 h period of milk stasis. The rate of mammary fatty acid synthesis in vivo determined using tritiated water was not significantly altered by 12 h of milk stasis, and analysis of the milk and gland fatty acids showed that the relative proportions of de novo synthesized fatty acids (medium-chain fatty acids) and those derived from the circulation (16 and 18 C acids) had been maintained. Light and electron microscopy showed the accumulation of considerable quantities of lipid within the lumen of the alveoli even while the pups were still suckling. Twelve hours after the removal of the pups there was not only a marked increase in the lumenal lipid, but also considerable lipid trapped in the epithelial cells. In rats where the nipples were ligated unilaterally and allowed to be suckled for 12 h, the milk from the ligated glands contained significantly less lipid than that from the suckled glands but more lipid than from milk of rats removed from their pups for 12 h. Administration of oxytocin during 12 h of milk stasis significantly increased the milk lipid content.
 ...
PMID:Milk lipid synthesis and secretion during milk stasis in the rat. 376 Oct 33

Ewes carrying twin fetuses were maintained during late pregnancy on a uniformly high plane (n = 22), a uniformly low plane (LP) (n = 24) or a low plane increasing to a high plane (n = 14) of nutrition. Seven ewes at each nutritional level were killed at 142 days of gestation and the liver and muscle glycogen and body lipid concentrations of the fetuses were determined. The rest of the ewes lambed naturally at about 145 days and the colostrum yields were obtained by hand milking after oxytocin injections during the first 18 hours after birth. The lactose, lipid and protein concentrations of colostrum were determined. Undernutrition in the LP group did not apparently affect the body concentrations of available glycogen, reduced available body lipid by about 47 per cent and reduced the lactose, lipid and protein available in colostrum during the first 18 hours by about 50 per cent. Refeeding previously underfed ewes to a high plane during the last five to 10 days of pregnancy did not improve the available reserves of glycogen or lipid in the lambs but did increase the yields of colostral constituents by about 30 per cent. The relative contributions of body reserves and colostral constituents to the maintenance of high, medium and low metabolic rates in lambs from different groups was assessed. It was concluded that under normal field conditions refeeding undernourished ewes during the last weeks of pregnancy would improve only marginally the survival potential of the lambs and that most lambs would be compelled to draw on their body glycogen reserves in order to maintain heat production during the first 18 hours after birth, even when they consumed all the available colostrum.
 ...
PMID:Effects of maternal nutrition on the availability of energy in the body reserves of fetuses at term and in colostrum from Scottish Blackface ewes with twin lambs. 407 Jul 90


1 2 3 4 5 Next >>