ABSTRACT
In fasted and fed states, blood insulin levels are oscillatory. While this phenomenon is well studied at high glucose levels, comparatively little is known about its origin under basal conditions. We propose a possible mechanism for basal insulin oscillations based on oscillations in glycolysis, demonstrated using an established mathematical model. At high glucose, this is superseded by a calcium-dependent mechanism.
Subject(s)
Islets of Langerhans , Calcium/metabolism , Glucose/metabolism , Glycolysis , Humans , Insulin/metabolism , Insulin Secretion , Islets of Langerhans/metabolismABSTRACT
This study monitors changes in urinary excretion of water and minerals before and after exercise in pre-menopausal women and in those using oral contraception. Resting urine flow rate was lower and sodium output significantly higher (p less than 0.02) during the normal post-menstrual phase than during other phases of the cycle. These changes were unrelated to glomerular filtration rate and might impede maximal performance. After exercise an oliguria and hyponatriuresis were most pronounced during the menstrual phase. In addition the resting urinary output of calcium and magnesium were unrelated to normal oestrogenic and progestegenic cyclic surges. Amongst oral contraceptive users, resting excretion of water, minerals and creatinine were all significantly lower than general menstrual cycle values (p less than 0.01) and further reductions in salts and water output occurred with exercise. Basal calcium and magnesium excretion rates were significantly lower than general menstrual cycle values (p less than 0.05). Renal conservation of water and salts for 'pill' takers may affect renal homeostasis. The consequences of mineral retention are unknown.
