URINE PRODUCTION-RATE AND RENAL BLOOD-FLOW IN THE NEAR-TERM OVINE FETUS ARE NOT RELATED TO HIGH AND LOW-VOLTAGE ELECTROCORTICAL ACTIVITY

Studies in both the human and ovine near-term fetus have identified th e clustering of physiologic and behavioral parameters into states. In a recent study in the human fetus a considerable decrease was found in fetal urine production during nonrapid eye movement (non-REM) compare d with REM sleep. Whether this decrease was caused by decreased renal blood flow or changes in urine concentration is not known. This prompt ed us to investigate the relation between fetal urine production rate and electrocortical activity in the near-term ovine fetus. We hypothes ized that in the ovine fetus urine production and renal blood flow dur ing REM [comparable to low voltage electrocortical activity (LV ECoG)] would be lower than during non-REM [(high voltage (HV) ECoG)]. In eig ht fetal sheep between 123 and 127 d of gestation (term 147 d), ECoG, renal blood flow, urine flow, and urine osmolality were measured conti nuously for 6 h on 2 consecutive days. Data were analyzed into HV ECoG and LV ECoG whereafter urine flow, urine osmolality, and renal blood flow data were averaged per state. We found no significant differences in urine flow, urine osmolality, or renal blood flow between the two behavioral states in the ovine fetus. Because these data are in sharp contrast to those found in the human fetus, we conclude that the obser ved dissimilarities in renal responses between the human and sheep fet us add to the already known differences in behavioral states between t he two species.