Effect of Acute Changes in Serum Calcium on Glucose Tolerance, Blood Glucose, IRI and Cortisol Levels

Abstract

151According to experimental data calcium ions are involved both in the secretory process (Grodsky and Bennett 1966, Mi/ner and Haies 1967, Malaisse and Malaisse-Lagae 1970_and the action of imulin (Kissebah, Hope-Gill, Vydelingum, Tulloch, Garke and Fraser 1975). Since only a few cJinicai observations have been reported on this subject so far, it seemed worthwhile to investigate the effect of an altered serum calcium on glucose tolerance, blood glucose and IRI levels. Materials and Methods11 diabetics -treated with diet or diet + antidiabetic drugs and 53 non-diabetics were investigated: all the diabetics and 46 of the non-diabetics (normal group) received 10%, caa 2 (3.6 mg Ca++/kg b.w.) intravenously. Blood was taken before and 5,15,30,60, 120 and 180 minutes after the i.v. injection for the determination of serum calcium (Ray Sarkar and Chau· han 1967), glucose (o-toluidin method), IRI (Amersham-KIT, double antibody technique of Haies and Randle 1963), and cortisol (fluorimetric method of Mattingly 1962), 7 of the non-diabetics served as controls: their blood glucose and cortisol were measured without previous calcium load.A self-controlled mathematical analysis was carried out using Student's t test. AU the changes were compared to the initial (zero minute) values and the means were given within the 95% fiducial limits: i( ± t(0.5) . si(' In a further study 50 g oGTT was performed in five hypocalcemic patients (see Table). Three days later the oGTT was repeated with a simultaneous i.v. caa2 injection (3.6 mg Ca++/kg b.w.). Blood sugar and IRI were determined from venous blood sampies at 0, 15, 30, 60 and 120 minutes. IRI

Potentiation of glibenclamide-induced insulin release by calcium infusion

“…Similar findings have been reported by Rizvi et normal glucose disappearence and insulin secretion in azotaemic, hypocalcaemic subjects, and in a subgroup of their patients insulin secretion was even reduced by calcium infusion [14]. In our earlier study the insulin response to oral glucose load in chronically hypocalcaemic patients was normal and unaffected by calcium injection [3]. Recently Harter has demonstrated that in Parathyroid hormone-treated dogs glucose-stimulated insulin release was increased by hypophosphataemia, but not by hypercalcaemia.…”

The Effect of Serum Ionized Calcium Elevation on Somatostatin Inhibition of Glucose‐induced Insulin Release in Humans

“…glibenclamide (Gero et al, 1977) whereas hypocalcaemia has been associated with decreased insulin responses to glucose (Yasuda et al, 1975;Rizvi et al, 1975) and arginine (Laron & Rosenberg, 1970). On the other hand, reports by other investigators have not found this positive correlation of serum calcium levels and insulin responses (Lisch e l al., 1973;Gero et al, 1976). The explanation for these contradictions are not apparent at the moment.…”

Insulin secretion after oral calcium load.

“…Maximum blood sugar level (Max BS), maximum serum IRI (Max IRI), maximum rise of blood sugar level from the fasting state (Max dBS), maximum rise of serum IRI from the fastine level (Max JIRI). maximum levels without a significant change in serum IRI (Gero et al, 1976). In patients with islet cell tumor, intravenous calcium infusion caused a release of insulin and proinsulin, but no such effect was obtained in normal subjects (Gaeke et al, 1975).…”