A STUDY OF NEPHRON FUNCTION IN NORMAL TROPICAL RESIDENTS USING THE CREATININE AND LITHIUM CLEARANCES

The kidney bears the brunt of the demands of a tropical climate for wa ter and electrolyte homeostasis. We hypothesised that a tropical clima te may cause adaptive changes in the entire organism leading to altere d renal function in our subjects. Hence renal function data for reside nts of a temperate climate may not be applicable to tropical residents . We therefore sought to elucidate renal function in subjects residing in a tropical climate. We used lithium clearance, C-Li, a non-invasiv e tool for assessing proximal tubular function in humans, and endogeno us creatinine clearance, C-Cr, to estimate proximal tubular function a nd glomerular function, respectively, in our subjects. We did this in order to establish whether or not nephron function in our subjects dif fers from that for residents of a temperate climate. Nineteen male and 12 female Ghanaian subjects aged between 15 and 48 years were studied . The estimated G(Cr) was 117.3+/-6.6 ml/min for male subjects and 97/-6.4 ml/min for female subjects. C-Li was 20.3+/-1.6 ml/min for male and 19.1+/-0.4 ml/min for female subjects, respectively. The estimated absolute reabsorption rate of fluid of proximal tubules was 97.0+/-6. 0 ml/min for males and 78.1+/-6.0 ml/min for females. The percentage p roximal fluid reabsorption for male and female subjects was 81.2+/-1.4 and 79.5+/-1.6, respectively. The differences between male and female values (mean+/-SEM) were not statistically significant. The data sugg est that the proximal tubule in residents of a tropical climate may re absorb more fluid compared to that in residents of a temperate climate . Our values for proximal tubular reabsorption are higher than those r eported for residents of a temperature climate. Our estimate of glomer ular filtration, however, is similar to published data for Caucasians. The difference in proximal tubular function may reflect possible rena l adaptation to a hot, humid climate. We conclude that renal function of tropical residents differs from that of residents of a temperate cl imate. This difference may be due to renal adaptation to the hot, trop ical climate.