Adrenomedullary and glycemic responses to ACTH, corticosterone, aldosterone, epinephrine and norepinephrine administrations in the soft-shelled turtle
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The aim of the current investigation was to ascertain the role of ACTH and adrenal hormones on adrenomedullary and glycemic functions in soft-shelled turtles, Lissemys punctata punctata. All the experiments were carried out on sexually immature animals. Findings revealed that: (1) ACTH administration (0.5 IU/1.0 IU/2.0 IU per 100 g body wt. daily for 10 days) in all doses stimulated adrenomedullary function by increasing medullary cell nuclear diameter with elevations of norepinephrine, epinephrine and blood sugar levels. Only moderate and higher doses (50 mug/100 mug per 100 g body wt. daily for 10 days) of dexamethasone suppressed adrenomedullary activity and blood sugar level by reversing the changes to those of ACTH; the responses were dose-dependent. But these changes were no longer observed after ACTH treatment in dexamethasone (DMS) recipients (DMS: 100mug / 100 g body wt daily for the first 10 days and ACTH: 0.5 IU / 100 g body wt daily for the next 10 days); (2) Only moderate and higher doses (50 mug/100 mug per 100 g body wt daily for 10 days) of corticosterone increased adrenomedullary activity and blood sugar level and the responses were also dose-dependent. But aldosterone treatment in all doses (same as for corticosterone) had no significant effect on the adrenal medulla or blood sugar level; (3) Only moderate and higher doses of norepinephrine or epinephrine (same as for corticosterone) caused adrenomedullary atrophy with depletions of norepinephrine and epinephrine levels but elevated the glycemic level. The findings are briefly discussed.
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Prajna P. Ray, Histophysiology Laboratory, Department of Zoology, University of Calcutta, 35 Ballygunge Circular Road, Calcutta - 700019, India