Control of the levels of cAMP in the early phase after addition of catecholamines and the effect of insulin is discussed under consideration of own findings from experiments with isolated fat cells of the rat. Data on the kinetics of cAMP are interpreted in the light of results from several groups of a rapid activation of phosphodiesterase activity along with the adenylate cyclase system. Comparison of energy metabolism of fat cells with the formation of cAMP under conditions of near-maximal activation of the adenylate cyclase system by isoproterenol shows that about half of the cellular ATP turnover is used for information transfer. Insulin reduces cAMP concentrations in the presence of isoproterenol within one min of incubation when added either together with or after the catecholamine. Experiments with propranolol and the phosphodiesterase inhibitor, methyl isobutylxanthine suggest an effect of insulin on formation and breakdown of cAMP.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMedDate not supplied

Control of insulin-dependent diabetes with portable miniaturized infusion systems.

A method of insulin therapy that appears to achieve better control of diabetes than present conventional methods is the use of insulin infusion devices--either glucose-controlled feedback (closed-loop) systems or the preprogrammed (open-loop) infusion pump. In view of the problems with implantable glucose sensors, we have worked to develop a miniaturized, programmable infusion system. Its use in insulin-dependent diabetic patients to provide either intravenous doses or a continuous subcutaneous insulin infusion resulted in significant reductions in blood glucose levels, glycemic excursions and 24-h glucose excretion.

Blood Glucose↗

PubMedDate not supplied

Search for the most practical regular/NPH mixtures for type I diabetic patients.

After 2 wk of good control 9 type I diabetic patients were hospitalized and treated in a randomized fashion with different human insulin mixtures (regular: NPH), containing 10, 15, or 20% regular insulin. In the case of the 15:85% mixture, mean blood glucose was found to be in the range of 70-150 mg/dl. Significant differences occurred at certain time points between the curves obtained with the 10:90% and the 15:85% mixtures, and the 10:90% and the 20:80% preparations, respectively. Prolongation of the interval between hormone injection and start of breakfast from 30 to 45 min abolished the postprandial glucose excursion in the 15:85% and the 20:80% mixture, but not the 10:90% mixture.

Adolescent↗