Comparison of the effects of neurotensin and vasopressin on the adrenal cortex of dexamethasone-suppressed rats.

Neurotensin (NT) and vasopressin (AVP) share some similarities as far as their actions on the adrenal weight and secretion are concerned. The present study aimed to compare the in vivo chronic effect of these two peptides on the adrenal cortex of dexamethasone (Dx)-treated rats. NT or AVP were ip. infused at a rate of 2 micrograms/rat/d for 7 d. In the animals concomitantly treated with 15 micrograms Dx/100 g/d for 7 d, both NT and AVP partially prevented adrenal atrophy. AVP enhanced plasma aldosterone concentration (PAC), but not that of corticosterone (PBC). On the other hand, NT did not affect either PAC or PBC. In rats treated with 35 micrograms Dx/100 g/d for 14 d, neither NT nor AVP administered for the last 7 d exerted any effect on the adrenal weight. However, also under these conditions of profound adrenal atrophy AVP was still able to notably raise PAC, while NT was ineffective. Our findings indicate that the mechanism underlying the aldosterone secretagogue action of AVP does not require, unlike that of NT, the presence of ACTH. Moreover, in light of many recent literature data they could suggest the possibility that in vivo NT acts on the rat adrenal cortex via AVP.