Calcium requirement for stimulation of cyclic AMP accumulation in anterior pituitary gland by LH-RH

Abstract

Removal of Ca2+ from the incubation medium by addition of 2 mM ethylene glycol bis-(beta-aminoethyl ether)-N, N'tetraacetic acid (EGTA) leads to at least 75% inhibition of the luteinizing hormone-releasing hormone (LH-RH)-induced accululation of adenosine 3'5'-monophoshpate (cyclic AMP) in rat anterior pituitary gland in vitro. This inhibitory effect of EGTA is reversed by the addition of Ca2+. A half-maximal effect of Ca2+ on LH-RH--induced cyclic AMP accumulation is observed at 2-5 X 10-5 M free Ca2+. The LH-RH-induced LH and FSH release is completely dependent upon the presence of Ca2+ in the incubation medium, a half-maximal effect being measured at 1-2 X 10-4 M free Ca2+. The basal release release of LH is increased upon Ca2+ removal.