ABSTRACT
The beta-adrenoceptor blockade, slow inward calcium current blockade and calcium concentration decrease in perfusion solution were studied for their effect on cAMP oscillations during cardiac cycle in the isadrin-activated isolated heart of guinea pig. Isadrin activation (3 X 10(-8) M) of beta-adrenoceptors caused an increase of the cAMP concentration by 50% during the contraction. All the actions decreased an average level of cyclonucleotide in the myocardium as compared with isadrin and what is more, obsidan (10(-6) M) removed the cAMP oscillations almost completely, the hypocalcium solution (0.15 mM Ca2+) decreased their amplitude and duration, finoptin (3 X 10(-8) M) qualitatively changed the oscillation profile. The results obtained make it possible to suggest, that a change in the concentration of ionized calcium in myoplasma is one of the reasons inducing changes in the cAMP during the cardiac cycle.
Subject(s)
Calcium/pharmacology , Cyclic AMP/metabolism , Myocardial Contraction/drug effects , Propranolol/pharmacology , Verapamil/pharmacology , Animals , Female , Guinea Pigs , In Vitro Techniques , Isoproterenol/pharmacology , Male , Myocardium/metabolismABSTRACT
Experiments on rats have shown that administration of a synthetic analog of leucine enkephalin at a dose of 100 mg/kg did not change the content of the immunoreactive parathyroid hormone in the blood plasma, but eliminated the parathyroidin-stimulating effect on the cAMP concentration in the renal tissue and AP activity in the blood. We conclude that enkephalins do not influence the secretion and metabolism of the parathyroid hormone, but block its peripheral effects and stimulate thyroid C-cell function.
Subject(s)
Calcium/metabolism , Endocrine Glands/drug effects , Enkephalin, Leucine-2-Alanine/analogs & derivatives , Enkephalin, Leucine/analogs & derivatives , Alkaline Phosphatase/blood , Animals , Calcitonin/blood , Cyclic AMP/analysis , Enkephalin, Leucine/pharmacology , Epinephrine/antagonists & inhibitors , Kidney/analysis , Male , Parathyroid Hormone/antagonists & inhibitors , Parathyroid Hormone/blood , RatsABSTRACT
Experiments on rats have shown that administration of a synthetic analog of leuenkephalin at a dose of 100 mg/kg did not change the content of the immunoreactive parathyroid hormone in the blood plasma but removed the parathyroidin stimulating effect on the cAMP concentration in the renal tissue and AP activity in the blood. It is concluded that enkephalins do not influence the secretion and metabolism of the parathyroid hormone but block its peripheral effects and stimulate thyroid C-cell function.
