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Epinephrine- and prostaglandin-sensitive adenyl cyclase in mammary gland

1973; Elsevier BV; Volume: 321; Issue: 1 Linguagem: Inglês

10.1016/0005-2744(73)90094-6

1878-1454

Hans‐Peter Bär,

Neuropeptides and Animal Physiology

Adenyl cyclase was measured in 1000 × g particulate fractions obtained from homogenates of lactating mammary tissues, or of cells derived thereof by collagenase treatment. The enzyme from rat mammary cells was found to be stimulated by epinephrine average 1.7- to 1.8-fold) and fluoride (about 7-fold), activities and stimulation by hormones and NaF being very variable. Rabbit mammary cells yielded the bulk of adenyl cyclase in fractions of low centrifugal force (600 × g). The enzyme showed a maximum in activity around pH 8, and it was stimulated by various catecholamines (up to 3-fold) and prostaglandins (3- to 4-fold), Ka values for epinephrine and prostaglandin E1 being 0.1 to 0.3 μM and 1 μM, respectively. Caffaine and aminophylline reduced apparent activity in the presence of 1 mM 3′, 5′-AMP in assays. Storage of enzyme at 0 °C showed only small losses in activity or sensitivity to stimulation by epinephrine or fluoride. Propranolol inhibited stimulation by epinephrine, as expected for a competitive inhibitor. Alpha-blocking drugs like phentolamine and phenoxybenzamine also inhibited stimulation by epinephrine, although not in a competitive fashion. Maximally effective doses of epinephrine and prostaglandin E1 did not lead to additive stimulation. Adenyl cyclase from mouse mammary cells was not studied systematically; however, it was also shown to be stimulated by epinephrine and prostaglandins.