抄録
Platelet-activating factor (PAF) is a highly potent stimulator of the secretion of cortisol, corticosterone, and aldosterone. We previously reported that PAF acts mainly through PAF receptor accompanied by the activation of protein kinase (PK) C. While, ACTH acts through ACTH receptor accompanied by the activation of PK A. In the present study, we studied the cross-talk in adrenal steroidogenesis among PAF, ACTH, and angiotensin II (ANG II). 1) The administration of 1nM PAF or 10pg/ml ACTH significantly stimulated cortisol secretion. The rate of secretion peaked 2.5-5 or 10-12.5min after infusion of PAF or ACTH. When concurrently applied 1nM PAF with 10pg/ml ACTH evoked cortisol secretion less than additional and peaked 5-10min. 2) Aldosterone secretion in response to ANG II significantly stimulated at 1nM and peaked 15-20min after the infusion of ANG II. The administration of 10nM PAF did not induce significant aldosterone secretion. The concurrent administration of 1nM ANG II with 10nM PAF significantly inhibited the secretion of aldosterone to ANG II. 3) Aldosterone secretion in response to ACTH significantly increased at 1ng/ml and peaked 15-20min after the infusion of ACTH. The concurrent administration of 1ng/ml ACTH with 10nM PAF significantly evoked aldosterone secretion almost additional. The rate of secretion peaked 0-2.5min after infusion of the mixture. These results implicate that a cross-talk between the PK A system and the PK C system regulates the cortisol and aldosterone secretion. [J Physiol Sci. 2006;56 Suppl:S99]
