Charles P. Lucas

Studies on the partial isolation of human renin

Abstract Studies on the partial isolation of human renin have been described. We have observed that: 1. 1. Thorough disruption of the cell membranes by an all glass homogenizer increases the yield of enzyme eluted from renal tissue. 2. 2. QAE-Sephadex and calcium gel cellulose chromatography are valuable tools for the purification of renin. Gradient elution is superior in ion exchange chromatography of human renin. The properties of the final preparation obtained (Fraction 9) are: mol. wt. 42 000; isoelectric point pH 5.25; A280 mμ:A260 mμ = 2.1; pH optimum for human substrate 5.5; hog substrate 7.5–8.5; and tetradecapeptide renin substrate 5.5. Specific activity 8.4 Goldblatt units per mg protein (by bioassay in the dog). 3. 3. Evidence was obtained for the existence of considerable amounts of angiotensin I converting enzyme in human kidneys. Problems concerning the standardisation of human renin have been discussed.

Augmentation of Insulin Activity: Physiological Implications of a Property of Human Serum Revealed by Dilution

Dilution of human serum does not lead to the expected reduction of its insulin-like activity (ILA) as measured by the epididymal fat pad. Dilution of a solution of Crystalline Insulin does, however, reduce activity arithmetically. Because the addition of Crystalline Insulin to diluted serum results in levels of ILA greater than expected (augmentation), the failure of ILA to fall arithmetically with dilution may reflect this augmentation effect on endogenous ILA. The augmentation effect, as revealed by dilution and the addition of Crystalline Insulin, has been shown to increase in the serum of normal subjects after glucose loading, and to be deficient in fasting serum from the untreated diabetic patient.

Release of insulin-like activity from serum of normal subjects and diabetic patients

Exposure to acid-ethanol releases intense, previously masked insulin-like activity from the serum of both normal subjects and untreated diabetic patients. In proportion to the level of ILA in intact serum, diabetic serum contains less masked ILA than does normal serum. In terms of total ILA, however, that released from the serum of diabetics exceeds that released from normal serum, both in the fasting state and after glucose loading. The delayed increase of serum ILA after glucose loading, repeatedly observed in diabetics, has been shown to hold true for acid-alcohol releasable ILA as well.

A Plasma Inhibitor of the Renin-Antirenin Reaction and the In Vitro Generation of Angiotensin I

In the course of studies designed to develop a radioimmunoassay system for the detection of renin, we have identified in human plasma a potent inhibitor that interferes with the renin-antirenin reaction. Utilizing gel filtration, this renin-antirenin inhibitory activity was found to have the same molecular size as renin substrate. However, it could be separated from renin substrate by ion-exchange chromatography. When fractions containing this activity were tested in an in vitro system containing renin and renin substrate, they were found to inhibit the generation of angiotensin I.

A Globulin System from Human Serum that Augments the Activity of Crystalline Insulin on the Epididymal Fat Pad Deficiency in Diabetes Mellitus

It has been demonstrated that globulin isolated from normal serum augments the action of added crystalline insulin when assayed on the rat epididymal fat pad. This augmentation capacity is very low or absent in globulin from the serum of untreated diabetic patients. The possibility is discussed that these findings may indicate that diabetic patients produce an abnormal form of insulin.

FURTHER STUDIES ON INSULIN AUGMENTATION CAPACITIES OF VARIOUS SERUM PROTEINS.

Abstract The ability of human serum protein to augment the action of crystalline insulin on the epididymal fat pad has been further evaluated. Serum proteins were fractionated by elution from DEAE cellulose and the capacity of individual fractions to augment insulin action determined. The property was found to be present in all fractions, but concentrated to a slightly greater extent in the fastermoving gamma globulins and beta globulins. The augmentation effect has again been found to be deficient in diabetes mellitus.

Some characteristics of the insulin augmentation phenomenon

Abstract A serum protein fraction possessing the capacity to augment insulin action on adipose tissue in vitro has been isolated and studied. Factors responsible for augmentation have been found to be nondialyzable and susceptible to destruction by ethanol, alkali and heat. The augmentation phenomenon is probably dependent upon the presence of a protein moiety.