Marvin J. Yiengst

Age Changes in Heart Rate and Blood Pressure Responses to Tilting and Standardized Exercise

Tilting and standardized exercise caused extensive shifts of heart rate and auscultatory blood pressures in 140 ambulatory male subjects from 20 to 92 years of age. Following similar exercise, the older subjects showed a greater increase of heart rate and pulse pressure than did the younger subjects who compensated the changes caused by tilting more completely and rapidly than did the older subjects. These slower compensatory responses of older subjects should be considered in the interpretation of metabolic recovery rates after exercise.

The glomerular clearance and renal transport of hemoglobin in adult males.

The demonstration by Polonovski, Jayle, Boussier and Badin (1, 2) that certain plasma proteins have the property of binding extracorpuscular hemoglobin has led to recent re-evaluation of the mechanisms of renal transport of hemoglobin in the dog (3) and in man (4). Lathem (4) showed that circulating extracorpuscular hemoglobin is bound quantitatively to the a2-globulin, haptoglobin. By utilizing the infusion of autogenous hemoglobin solution, Lathem demonstrated that in man: 1) no unbound hemoglobin is found in the circulation until the plasma hemoglobin-binding capacity is saturated; 2) hemoglobinuria does not occur unless unbound hemoglobin is present in the circulation; and 3) neither protein-bound hemoglobin nor methemalbumin appears in the urine during hemoglobinuria. From the relationship between changing concentration of unbound hemoglobin in the plasma (APfree Eb) and urinary excretion rate (ZAUfree HbV) an estimate of the glomerular clearance of hemoglobin (CGfree Hb) may be obtained. As defined by Lathem (4), glomerular clearance of free hemoglobin =AUfree HbV/APfree HbPrevious studies from this laboratory (5, 6) have demonstrated a sytematic decrease in glomerular filtration rate, effective renal plasma flow and various tubular transport maxima with age. A progressive loss of whole nephrons with aging has been proposed (5). Little is known of the effect of aging on the permeability characteristics of the glomerular membrane. Everitt (7) has reported a tenfold increase in the daily excretion of urinary protein nitrogen from youth to senility in the rat. Studies in mice by Thung (8) have demonstrated both qualitative and quantitative changes in proteinuria in older animals, .but the relationship of these changes to glomerular perme-

Natriuresis and Carbohydrate-Induced Antinatriuresis after Overnight Fast and Hydration

Following an overnight fast and oral hydration, some normal individuals developed a marked natriuresis. This renal salt wasting could be promptly curtailed by the ingestion, or in some cases, infusion of glucose. Infusion of insulin alone also was capable of decreasing urinary sodium excretion. Older subjects appeared more prone to develop an exaggerated natriuresis following fasting and hydration and developed more striking salt retention following carbohydrate ingestion than did younger subjects. Young subjects, restudied after longer periods of fasting (36 hours), still failed to develop a natriuresis following hydration. The hypothesis that the hyponatremia in acutely and chronically ill patients might develop, at least in part, as a result of excess salt loss during periods of inadequate carbohydrate intake was tested. Acutely and chronically ill patients, many with mild hyponatremia, failed to develop inappropriate salt loss with overnight fast and hydration. These findings failed to support this hypothesis.

Effect of lactate on renal tubular transfer of p-aminohippurate in man.

Summary The intravenous administration of sodium lactate causes a statistically significant increase in TmPAH in man. The average maximum increase amounted to 30% of the preinjection levels, and the effect was observed in each of 8 subjects tested twice. Neither the observed increases in pH8 and (BHCO3) nor the changes in renal blood flow appear to bear a causal relationship to the increases in TmPAH produced. The technical assistance of Mrs. Elsie Beard, Miss Margaret McCollum, Mr. Arthur Dinan, and Mr. W. Irving Jones is gratefully acknowledged.