Effects of homologous natriuretic peptides in isolated skin of the bullfrog, Rana catesbeiana

Abstract

The effects of frog atrial (fANP), brain (fBNP) and C-type natriuretic peptide (fCNP) on transepithelial ion transport were investigated in the bullfrog, Rana catesbeiana. The transepithelial potential difference (PD) and short-circuit current (Isc) of the abdominal skin were measured according to the technique of Ussing and Zerahn. When the abdominal skin was exposed to homologous natriuretic peptides (NPs) at concentrations ranging from 4×10 −13 to 5×10 −7 M, no significant changes in PD or Isc were observed. The influence of the NPs on the arginine vasotocin (AVT)-induced increase in Isc was then examined. Treatments with ANP and BNP (4 ×10 −9–4×10 −8 M) inhibited the increase in the AVT (10 −8 M)-induced Isc. Furthermore, fCNP I and fCNP II (5×10 −13–5×10 −7 M) did not significantly inhibit the increase in the AVT-induced Isc. The cyclic GMP analog, 8-BrcGMP, (>10 −4 M) with AVT inhibited the increase of AVT-induced Isc, as well as fANP and fBNP. HS-142-1, an inhibitor of particulate guanylyl cyclase, (10 −5 g ml −1) significantly reduced the inhibitory action of fANP on the increase of AVT-induced Isc. These results suggest that fANP and fBNP act through the guanylyl cyclase systems to increase cellular cGMP and modulate AVT-induced epithelial transport in a concentration-dependent manner. It is also suggested that fCNPs have no effect on the natriferic response in the skin of the bullfrog.