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.