Biology of Reproduction, Vol 15, 297-302, Copyright © 1976 by Society for the Study of Reproduction

Rate of Formation and Osmolality of Oviductal Fluid in the Cycling Rat

¹ Division of Reproductive Biology, Department of Population Dynamics, School of Hygiene and Public Health, The Johns Hopkins University, Baltimore, Maryland 21205

The rate of formation and osmolality of oviductal fluid in anesthetized 4-day cycling Sprague-Dawley rats have been studied using micro and ultramicro techniques adapted from those used in renal physiology. The rate of production of oviductal fluid was found to vary with the stage of the estrous cycle. The highest rates were observed on proestrus (84 nl/min) and estrus (81 nl/min). The rate decreased to 56 nl/min on diestrus Day 1 and further to 32 nl/min on diestrus Day 2. These results are in qualitative agreement with the work of others in larger mammals in which it has been demonstrated that the rate of oviductal fluid production is greatest at estrus and reduced at other stages of the cycle and during pregnancy. In paired experiments the osmolalities of simultaneously collected arterial plasma and oviductal fluid samples have been compared. Neither plasma nor oviductal fluid osmolality vary during the estrous cycle. Thus, the data have been pooled. The mean values for the plasma and oviductal fluid are 290 ± 1 (SEM) and 287 ± 1 mOsm/kg H₂O. A small but highly significant difference was found between the paired plasma and oviductal fluid osmolalities, (OF/P)_OSM = 0.989 ± 0.004 (P<0.005). The physiological significance of this small difference is not known.

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ACKNOWLEDGMENTS The advice and encouragement of W. J. Brunton is gratefully acknowledged. C. Velez and D. Samson provided valuable technical assistance.