Agnes M. Huber

The effect of fasting and refeeding on isolated rat adipose tissue activity in the presence of crystalline and “bound” insulin

Effects of crystalline and “bound” insulinobtained from human serum on net gas exchange and fat synthesis from glucose by isolated epididymal adipose tissue from fed, fasted and fasted, refed rats have been studied. Fasting resulted in a marked decrease in activity of epididymal adipose tissue in the presence of either crystalline or “bound” insulin. Refeeding rats after a 4 day fast resulted in hyperactivity of their adipose tissue to both forms of insulin which remained maximal after 7 days of repletion. Positive net gas exchange was immediate and linear when adipose tissue from fed and fasted, refed rats was incubated with crystalline insulin and when adipose tissue of fasted, refed rats was incubated with “bound” insulin. A delay in response was observed when adipose tissue of fasted rats was incubated with either form of insulin or when the adipose tissue of fed rats was incubated with “bound” insulin. It has been suggested that epididymal adipose tissue has the ability to modify the activity of crystalline or “bound” insulin and that it does this in response to the metabolic state of the animal.

Responses of obese-hyperglycemic mice and normal mice to 'bound' and crystalline insulin.

Abstract The effects of bovine crystalline insulin and “bound” insulin obtained from human serum on glucose utilization in intact obese-hyperglycemic mice and their nonobese siblings and on their isolated epididymal adipose tissue have been studied. “Bound” insulin showed activity similar to that of crystalline insulin in control mice. It stimulated the incorporation of glucose into diaphragm glycogen in vivo and into epididymal adipose tissue glycogen and fat in intact mice and isolated epididymal fat pads. The utilization of glucose by obese-hyperglycemic mice was depressed when compared to controls in the presence of “bound” or crystalline insulin. In older obese and control mice, their ability to synthesize epididymal adipose fat decreased. The formation of diaphragm glycogen also decreased with age in the obese but not control mice.

The Effect of Duration of Alcohol Administration on the Deposition of Trace Elements in the Fetal Rat

It is postulated that the effect of alcohol on trace element deposition during pregnancy is a long term one, requiring alcohol administration throughout the 21 days of gestation. Female Charles River rats (N = 30) were given a semi-synthetic diet throughout pregnancy. Half the animals received alcohol (8 ml/kg) by esophageal tube, the other half were sham operated. Within each group, animals were treated for one, two or three weeks beginning with day 0. Dams and pups were sacrificed following a natural delivery. Iron (Fe), copper (Cu), zinc (Zn), and magnesium (Mg) were measured in maternal and fetal tissues by atomic absorption spectrometry. The results indicated an increased fetal level of Zn, Mg, and Fe in all groups treated with alcohol. Increased fetal levels of Cu were found in the group treated for three weeks with alcohol. No differences were found in maternal tissue levels. These changes in fetal levels correspond to the effect of alcohol on gestation. Alcohol-treated litters were anywhere from 2 to 6 days overdue, providing a longer time period in utero for nutrient uptake.

Evidence of an Insulin Inhibitor in Human and Rat Serum.

Summary Greater insulin-like activity was observed in dialyzed rat and human sera than undialyzed sera, using an isolated rat epididymal adipose tissue insulin assay technique. Dialysates from both rat and human sera decreased the activity of rat epididymal adipose tissue in the presence of crystalline insulin.

In vitro Effects of Zinc on Insulin Activity in Adipose Tissue.

Summary Zinc in concentrations in the range of those observed in human plasma and higher inhibited the activity of isolated rat epididymal adipose tissue in the presence of insulin and glucose. Of the other divalent ions studied only mercuric and to a lesser extent cobalt and nickel ions inhibited insulin activity. Zinc inhibition could be prevented in part by dialysis at pH 3.75 but not 7.6. The inhibition by zinc could be prevented by EDTA or large amounts of phosphate. The authors wish to thank Mrs. Zalfa Sayejrh and Miss Eileen Foster for their technical assistance.