Elasmobranch renin angiotensin system and the angiotensin receptor

The presence of specific angiotensin II (ANG II) receptors has been demonstrated in a number of different tissues in elasmobranch fish both in membrane fractions and by quantitative in vitro autoradiography using homologous I-125-labelled dogfish ANG II. Specific binding was greatest in the interrenal gland and significant binding also occurred in the gill, rectal gland and intestine. The receptors in the Sill and rectal gland appear to be AT(2)-like based on displacement of labelled dogfish ANG II with the AT(2) receptor antagonist CGP 42112. The receptor in the interrenal gland showed equal displacement to both AT(1) and AT(2) antagonists. The presence of ANG II receptors in osmoregulatory tissues suggests that RAS may play an important role in controlling water and electrolyte balance in clasmobranch fish.</p

Evidence for the intrarenal renin-angiotensin system in the European lesser-spotted dogfish

The existence of an intrarenal renin-angiotensin system (RAS) in a perfused European lesser-spotted dogfish Scyliorhinus canicula trunk preparation was examined by the inhibition of angiotensin-converting enzyme by captopril. This resulted in a glomerular diuresis, an increase in urea and chloride clearance and excretion, and an increase in transport maxima for glucose. It is proposed that these results suggest the presence of an intrarenal RAS. (C) 2003 The Fisheries Society of the British Isles.</p

The dipsogenic effect of the renin-angiotensin system in elasmobranch fish

This study investigated the control of drinking in elasmobranch fish through manipulation of the homologous renin-angiotensin system (RAS). The smooth muscle relaxant papaverine was found to increase basal drinking levels in the European lesser-spotted dogfish, Scyliorhinus canicula, almost 20-fold. However, this response was significantly reduced with the coadministration of the angiotensin-converting enzyme inhibitor captopril which had no effect when administered alone. Captopril was also found to block a 7-fold increase in drinking rate following administration of homologous angiotensin I in S. canicula. Finally, administration of homologous angiotensin II produced a dose-dependent response in drinking rate in two species of elasmobranchs, S. canicula and the Japanese dogfish, Triakis scyllia. These results demonstrate a central role of the RAS in the control of drinking in elasmobranch fish. (C) 2001 Elsevier Science.</p