No abstract

SUMMARY1. 42K efflux has been measured from small strips of turtle sinus venosus tissue in order: (a) to characterize further the pharmacology of the acetylcholine response and (b) to test whether cyclic guanosine 3': 5'-monophosphoric acid (cyclic GMP) is the intracellular mediator of this response.2. The 42K wash-out curves show that the fractional escape rate (FER) of 42K efflux is nearly constant after 60-80 min, indicating that after this time period 42K FER is controlled by barrier-limited diffusion from a single intracellular compartment.3. The threshold of the dose-response relationship for the acetylcholine-induced increase in 42K FER is about 10-8 M and the Km is 2'75 x 10-7 in non-eserinized preparations.4. This acetylcholine response is completely blocked by atropine; but nicotinic blockers produce no detectable reduction of it. 5. Exogenous application of lipid-soluble analogues of cyclic GMP (dibutyryl or 8-bromo-cyclic GMP applied at 2-3 mm for 30 min) failed to mimic the acetylcholineinduced augmentation of 42K FER. 6. Experiments in which sodium nitroprusside (5 x 10-4 M for 30 min) was applied in order to stimulate the guanylate cyclase and hence produce a large, maintained increase in intracellular cyclic GMP failed to show a significant increase in 42K FER.7. When acetylcholine (10-6 M) was applied in the presence of O[Ca2+]o (in an attempt to inhibit the guanylate cyclase) there was no significant reduction in the acetylcholine-induced increases in 42K FER.8. Hence, these three indirect tests indicate that the muscarinic acetylcholineinduced increase in 42K FER in cardiac pace-maker tissue is unlikely to be mediated entirely by changes in the levels of intracellular cyclic GMP.

In the male rat a diet rich in beef fat facilitates the occurrence of hyper-insulinemia after a glucose load whereas fats rich in linoleic acid produce no such effect. The combination of saturated fat and saccharose facilitates the occurrence of hyper-triglyceridemia in the male rat, no such effect is produced by the combination of fats rich in linoleic acid and saccharose. Linoleic acid prevents natrium chloride from provoking hypertriglyceridemia in male and in female rats subjected to a diet enriched in saccharose and fat. Estrogen-induced hypertriglyceridemia in castrated animals is strongly inhibited if the diet is rich in linoleic acid. Physical effort can prevent saccharose combined with saturated fats from inducing hypertriglyceridemia.

No abstract

No abstract