Increase in pituitary adenosine 3′:5′-cyclic monophosphate content and potentiation of growth-hormone release from heifer anterior pituitary slices incubated in the presence of 3-isobutyl-1-methylxanthine

摘要

pThe release of growth hormone from heifer anterior pituitary slices and the cyclic AMP content of the slices were increased by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine, both increases being related to inhibitor concentration over the range 0.1–1.0mm. Neither Basup2+/sup(6.9 or 2.3mm), Ksup+/sup(72mm), nor ip/i-chloromercuribenzoate (20μm) had any effect on pituitary cyclic AMP content over a 20min period. 3-Isobutyl-1-methylxanthine potentiated the release of growth hormone in response to Basup2+/sup(2.3mm) and Ksup+/sup(24mm), but the degree of potentiation did not depend on inhibitor concentration in the same way as did tissue cyclic AMP content. 3-Isobutyl-1-methylxanthine decreased the concentration of Ksup+/suprequired to give maximum stimulation of growth-hormone release, but did not significantly increase the maximum response to Basup2+/sup. Growth-hormone release in the presence of prostaglandin Esub2/sub (1μm) was increased by 3-isobutyl-1-methylxanthine and was inhibited by the prostaglandin antagonist, 7-oxa-13-prostynoic acid, although this antagonist increased the pituitary cyclic AMP concentration and potentiated the prostaglandin Esub2/sub-induced rise in cyclic AMP content. The stimulation of growth-hormone release by ip/i-chloromercuribenzoate was not potentiated by 3-isobutyl-1-methylxanthine. The data suggest that Basup+/supand Ksup+/supact at the same point in the secretory process as 3-isobutyl-1-methylxanthine, although by a different mechanism, and that ip/i-chloromercuribenzoate has a different point of action./p