Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.4.4 (adenosine deaminase)
 5,136 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have examined the effects of some analogues of adenosine upon the circadian rhythm in rate of thymidine incorporation by cultured chick pineal glands. Incorporation in the early period of the photoperiod on day 2 of culture was slightly inhibited by the adenosine analogue N-ethylcarboxamido-adenosine, but this effect was not countered by the antagonist 8-phenyl-theophylline. Thymidine incorporation was inhibited when glands were continuously exposed to the adenosine transport inhibitor nitrobenzyl-thioinosine, but ongoing incorporation was not inhibited by addition of this agent. Removal of adenosine and deoxyadenosine supplements from the medium, with or without further addition of adenosine deaminase, had no appreciable effects upon thymidine incorporation. We conclude that adenosine and analogues probably play no role in regulation of the rhythm in rate of thymidine incorporation.
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PMID:Purinergic receptors have no major role in control of the circadian rhythm in rate of thymidine incorporation by cultured chick pineal glands. 192 41

Deoxyadenosine (dAdo) levels above 2 microM inhibit plasma cell (PC) differentiation by human blood lymphocytes in pokeweed mitogen (PWM) stimulated cultures containing deoxycoformycin (dCF), a potent inhibitor of adenosine deaminase (ADA). ADA inhibition by dCF alone did not suppress PC differentiation. Thymidine uptake by T cell blasts continuously cultured in conditioned medium was inhibited by dAdo and dCF; two of five EBV-infected B cell lines were also inhibited while three were resistant. Inhibition of PWM-induced PC differentiation of B cells by dCF and dAdo was reversed when conditioned medium (a source of T cell helper factors) was added to the cultures, and dAdo and dCF added to PWM-stimulated cultures 48 hr after their initiation did not inhibit PC differentiation, though thymidine uptake and the total number of cells recovered from the cultures were reduced. Removal of T cells after 48 hr of culture slightly reduced the numbers of PC in PWM-stimulated lymphocyte cultures but no further inhibition was obtained when dCF and dAdo were added to these T-depleted cultures, nor was their thymidine uptake further reduced. These results suggest that the in vitro suppression of B cell differentiation by dAdo in PWM-stimulated cultures is not due to direct toxicity of purine nucleosides to B cells but may be due to interference with T cell help. This is consistent with the view that a relative lack of helper activity by T cells contributes to the antibody deficiency of patients with ADA deficiency.
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PMID:Resistance of pokeweed mitogen-stimulated B cells to inhibition by deoxyadenosine. 696 49

Several endogenous factors generated within the vessel wall have been implicated in contributing to the vascular remodeling process associated with hypertension and atherosclerosis. Furthermore, substances generated by smooth muscle cells (SMCs) are known to regulate SMC proliferation in an autocrine fashion. Adenosine is a vasodilator synthesized by SMCs, and exogenous adenosine inhibits SMC proliferation. However, whether adenosine produced endogenously has antimitogenic effects is not known. Hence, we evaluated the effects of SMC-derived adenosine on 2.5% fetal calf serum-induced proliferation of rat aortic SMCs. SMC proliferation was assayed by measurement of DNA synthesis ([3H]thymidine incorporation) and cell counting. To determine the effects of endogenous adenosine on SMC proliferation, we stimulated growth-arrested SMCs with 2.5% fetal calf serum in the presence and absence of modulators of adenosine levels, including (1) erythro-9-(2-hydroxy-3-nonyl)adenine hydrochloride (EHNA; inhibits adenosine deaminase), (2) dipyridamole (blocks adenosine transport and inhibits phosphodiesterase), (3) dipyridamole plus EHNA, and (4) adenosine with or without EHNA. [3H]Thymidine incorporation and cell number were measured after 24 and 96 hours, respectively. EHNA and dipyridamole inhibited both FCS-induced DNA synthesis and cell proliferation in a concentration-dependent manner. Furthermore, extracellular (in medium) adenosine levels were significantly increased when cultured cells were treated with EHNA, and the inhibitory effects of dipyridamole as well as exogenous adenosine were enhanced in the presence of EHNA. Additionally, the inhibitory effects of dipyridamole and EHNA on DNA synthesis were significantly reduced in the presence of KF17837, an A2 adenosine receptor antagonist. These results indicate that SMC-derived adenosine can inhibit SMC proliferation. Hence, it is possible that a defect in localized adenosine synthesis within the vessel wall could contribute to vascular thickening and neointima formation.
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PMID:Smooth muscle cell-derived adenosine inhibits cell growth. 861 38