Hypocalcemic effect of homologous angiotensin-like substances produced by the renin-like enzyme in the corpuscles of stannius in the Japanese eel Anguilla japonica

Abstract In the intact Japanese eel kept in fresh water, a homogenate of the corpuscles of Stannius (CS) from the carp produces hypocalcemia when 50 mg/kg body weight of the tissue is injected intraperitoneally each day for 3 days. Angiotensin-like substances formed by incubating the eel CS extract with homologous plasma are also hypocalcemic when 250 ng equivalent to [Asp 1 , Ile 5 ]angiotensin II per kilogram body weight is injected according to the above schedule. Angiotensin-like substances formed by incubating the eel kidney extract with homologous plasma are less hypocalcemic. CS, plasma, and unicubated controls for CS angiotensin preparation are not hypocalcemic. They are made by eliminating plasma, CS extract, or incubation from the incubation mixture, respectively. This indicates that only the incubation product of the CS extract with plasma is hypocalcemic. When the CS secretes renin-like enzyme into blood, the enzyme may produce angiotensin-like substances in vivo . Formed angiotensin-like substances may cause hypocalcemia. Therefore, the present results suggest that the renin-like enzyme in the CS may be identical to hypocalcin in the Japanese eel.