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Biomedical subjects

S Shima

Publications and source records attributed to S Shima.

At least 163 records · Page 9Linked to original sources
PubMed1979

Effects of ACTH and calcium on cyclic AMP production and steroid output by the zona glomerulosa of the adrenal cortex.

Effects of ACTH and calcium on cyclic AMP production and steroid output by the zona glomerulosa (the capsular fraction) from the rat adrenal cortex have been studied. Although high concentrations of extracellular calcium potentiated the stimulatory action of ACTH on cyclic AMP and aldosterone output, tetracaine or verapamil inhibited aldosterone output but not cyclic AMP production during ACTH-stimulation. Lanthanum reduced both aldosterone and cyclic AMP accumulation induced by ACTH. These results suggest that an extracellular calcium would be essential in stimulating the capsular steroidogenesis without involvement of the cyclic AMP system.

Adrenal Cortex↗
PubMed1979

Studies on cyclic nucleotides in the adrenal gland. IX. Effects of ACTH on cyclic AMP and steroid production by the zona fasciculata-reticularis of the adrenal cortex.

Effects of ACTH and calcium on cyclic AMP and steroid production by the zona fasciculata-reticularis (the decapsulated fraction) from the rat adrenal cortex have been studied. Increasing concentrations of extracellular calcium enhanced the action of ACTH on cyclic AMP and steroid production. These effects of ACTH with calcium were prevented by lanthanum, but not by tetracaine or verapamil, suggesting that ACTH stimulation may be mediated by calcium through a process not involving the tetracaine- or verapamil-vulnerable step(s) of the calcium current. High concentrations of external calcium itself increased cyclic AMP accumulation without any increase in steroidogenesis. A calcium ionophore, X537A was stimulatory for steroidogenesis but inhibitory with respect to cyclic AMP accumulation. Considered together with the findings of AMP increase, these results suggest that ACTH primarily increases intracellular calcium mobilization thus stimulating directly the steroidogenesis, which is independent of the cyclic AMP system. Relatively high concentrations of ACTH activate the adenylate cyclase, which depends on extracellular calcium to increase cyclic AMP levels and stimulation of steroidogenesis by the decapsulated fractions of the adrenal cortex.

Adrenal Cortex↗
PubMed1978

Studies on cyclic nucleotides in the adrenal gland. VIII. Effects of angiotensin on adenosine 3',5'-monophosphate and steroidogenesis in the adrenal cortex.

Effects of angiotensin II on corticoid biogenesis and cAMP levels in the zona fasciculata-reticularis (the decapsulated fraction) and the zona glomerulosa (the capsular fraction) from the rat adrenal gland have been studied. Angiotensin II exclusively stimulated steroidogenesis in the zona glomerulosa without stimulation of the cAMP system, suggesting that steroidogenic action of this polypeptide does not involve the adenylate cyclase system. Angiotensin II was also found to stimulate cAMP-phosphodiesterase activity in the zona glomerulosa. An elevation of calcium concentration in the incubation medium has been observed to be effective in stimulating the production of aldosterone and cAMP by the capsular fraction. Angiotensin II caused a significant enhancement of the steroidogenic response of the capsular fraction to increasing calcium concentration regardless of the response of the cAMP system to calcium. This steroidogenic effect of angiotensin II was completely abolished by calcium antagonists added to the incubation medium without any inhibitory effect on the calcium-induced accumulation of tissue cAMP. These results suggest that angiotensin II acts on the adrenal II acts on the adrenal glomerulosa cell to increase intracellular calcium, which in turn directly stimulates steroidogenesis concomitant with the increased activity of phosphodiesterase.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1976

Studies on cyclic nucleotides in cancer. I. Adenylate guanylate cyclase and protein kinases in the prostatic sarcoma tissue.

Adenylate, guanylate cyclase and protein kinases in a fibrous sarcoma originating from rat prostate have been studied. A decrease in levels of adenosine 3', 5'-monophosphate (cyclic AMP) and adenylate cyclase activities and an increase in levels of guanosine 3',5'-monophosphate (cyclic GMP) and guanylate cyclase activities were observed in the tumor tissue when compared with the normal prostatic tissue of rats. Protein kinases from the tumor and the prostate were both responsive to exogenous cyclic AMP, with an apparent Ka of 0.08 muM in the tumor and of 0.11 muM in the prostate. It is of interest that the protein kinases from the tumor responded to cyclic AMP to the same extent as was observed in the enzyme preparation from the prostate. The protein kinase from the tumor was more sensitive to cyclic GMP than that from the prostate, showing an apparent Ka of 0.88 muM in the tumor and of 4.85 muM in the prostate. This tumor has been characterized with an increase in guanylate cyclase activities with a subsequent rise in cellular cyclic GMP and an increased sensitivity of the protein kinase to cyclic GMP.

3',5'-Cyclic-AMP Phosphodiesterases↗