Peptide hormone-stimulated second messenger production in the teleostean nephron

Renal actions of arginine vasotocin (AVT) and atrial natriuretic peptide (ANP) in teleosts are poorly defined. Administration of these hormones changes renal function, largely explained by systemic vascular effects. The present experiments examine the potential direct action of these hormones on the teleost nephron. This has been assessed from the hormones' abilities to stimulate their second messenger systems within isolated nephroi of the rainbow trout Onchorhynchus mykiss. Following initial experiments to define the experimental conditions, AVT was found to induce a dose-dependent increase in cAMP content of a suspension of nephroi incubated for 10 min at 10 degrees; 10(-5) M AVT provoking an increase of 846% (SW) and 829% (FW) above basal cAMP accumulation of 88 and 125 pmol/mg protein, respectively. This V2-type receptor response to AVT (or AVP) has previously been considered to be present only in the tetrapod kidney. ANP evoked a dose-dependent stimulation of cGMP accumulation from 1.3 (SW) or 1.9 (FW) pmol/mg protein basal levels to 5806 and 4405% of these levels, respectively, at the highest concentration used of 3.3 x 10(-7) M. Further experiments using isolated glomeruli from the eel Anguilla anguilla localized at least a part of the response to ANP to a glomerular site.