[Effect of insulin on respiration of rat mammary gland sections]

Effect of insulin on the respiration of rat's mammary gland slices was investigated at rest and during lactation. It was shown by means of polarographic technique that the rate of oxygen consumption in the mammary gland slices at rest is twice as low as during lactation. Addition of insulin (1.3 milliunits per 1 ml of the medium) to the slices of non-lactating mammary gland increases the respiration rate by 40%. No insulin stimulation of the respiration rate of the mammary gland slices during lactation was observed. The recorded fast response of the mammary gland tissue at rest to insulin may reflect different pattern of the relations between oxygen-dependent oxidation in mitochondria and oxidation of glucose in the pentose-phosphate cycle at different functional states of the organ. A conclusion is drawn as to possible demonstration of fast effect of insulin, unrelated to glucose transport, on the slices of rat's mammary gland at rest.