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Guanylate cyclase activity was examined in inflammatory granuloma tissue induced by subcutaneous injection of carrageenin solution in the rat. Enzymological properties of guanylate cyclase in this tissue, such as pH optimum, metal ion requirement, etc., were examined, with special reference to the intracellular distribution of the enzyme. Differences were found between guanylate cyclase in the soluble fraction and that in the particulate fraction in the response to Mn2+ and Triton X-100 in this tissue.

Treatment of rat reticulocytes with isoproterenol caused about 50, 25, and 25% decreases in beta-adrenergic agonist-, fluoride-, and guanine nucleotide-stimulated adenylate cyclase activities, respectively. The desensitization was also induced by dibutyryl adenosine 3',5'-cyclic monophosphate (cyclic AMP) and 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7) prevented the isoproterenol-induced desensitization, suggesting the involvement of cyclic AMP in the desensitization. Time course studies revealed that the desensitization to NaF-AlCl3 occurred faster than that to isoproterenol. Furthermore, the rate of the resensitization to NaF-AlCl3 by removal of isoproterenol was also faster than that to isoproterenol. Thus, it is likely that both guanine nucleotide-binding stimulatory regulatory protein, Ns, and beta-adrenergic receptor are sequentially involved in both desensitization and resensitization of the adenylate cyclase system in rat reticulocytes to isoproterenol.

The effect of dan-shen extract, the root of Salvia miltiorrhiza, on adenylate cyclase was investigated in both rat brain and rat erythrocytes. The EtOAc fraction of the MeOH extract was proved to have significant inhibitory activity. Potent inhibitory principles in the EtOAc fraction were isolated and identified as 4 polyphenolic acids, rosemarinic acid, lithospermic acid, and their methyl ester derivatives.

Involvement of divalent cations was examined in the activation of catecholamine sensitive adenylate cyclase in Ehrlich ascites tumor cells. In the presence of various concentrations of either Mg2+ or Mn2+, both basal and norepinephrine-stimulated, adenylate cyclase activities were measured. Both activities were gradually increased with the increase in Mg2+ concentration. On the other hand, with Mn2+, both activities were maximum at the low (2.5 mM) concentration, and decreased at the highest concentrations, the decrease being marked in the norepinephrine-stimulated activity. Similar difference between the two divalent cations was also observed in the effect on the binding of the beta-adrenergic ligand to the membrane receptor.

The effect of barbiturates on an adenylate cyclase system in rat brain was examined. The activity of the catalytic unit of this system isolated from the synaptic membrane was inhibited by phenobarbital in dose- and time-dependent manners. The mode of the inhibition was non-competitive with respect to Mg-adenosine triphosphate (ATP). The activity of the synaptic membrane-bound adenylate cyclase was also inhibited by phenobarbital in a similar manner. The inhibitory effect of phenobarbital was more potent on the activation of the enzyme by 5'-guanylylimidodiphosphate (GppNHp) than on the basal enzyme activity. The inhibitory effect, however, was not observed in the synaptic membrane preparation in which the guanine nucleotide-binding stimulatory regulatory protein (Ns) and the catalytic unit of adenylate cyclase system had been functionally coupled by pretreatment with GppNHp. Similar results were obtained with other pharmacologically active barbiturates. These findings indicate that barbiturates primarily affect the activation of the catalytic unit by an interaction with Ns resulting in the inhibition of the enzyme activity.