CELL-DENSITY, FLUID VOLUME AND ELECTROLYTE CONTENT OF BOVINE VULVAR TISSUE DURING ESTRUS AND DIESTRUS

Vulvar tissue hydration of oestrous and dioestrous lactating cows was studied by determining cell density (CD), dry matter (DM), total tissue water (TTW), extracellular water (ECW), and Na+ and Cl- concentrations in tissue biopsies. Na+, Cl- and osmotic concentrations (OC) in blood plasma were also determined. Each cow was biopsied during oestrus (Oe) and 10-13 days later (dioestrus, Di). CD (n = 4 cows) was determined in quick-frozen microscopic preparations. ECW (n = 9 cows) was determined by the 3H-inulin space method. During Di and Oe, the mean CDs were 43 and 25 cells/ng of mesenchymal tissue, respectively; the mean DM + TTW/cell (n = 17 cows) was approximately 74% greater in Oe than in Di. During Di, the mean DM, ECW and calculated intracellular water (ICW) were 24.2, 19.8 and 56.0 g/100 g tissue, respectively. During Oe, there was an absolute mean weight increase of 18.4, 38.0 and 17.6 g/100 g tissue in Di, in the DM, ECW and ICW, respectively. However, on a percentage basis, DM did not differ (24.5 vs 24.2%), ECW increased (33.2 vs 19.8%) and ICW decreased (42.4 vs 56.0%) during Oe vs Di, respectively. Plasma Na+, Cl- and OC were lower (P < 0.05) during Oe than during Di (Na+ = 123.1 ± 2.6 vs 130.9 ± 1.5 mEq/l plasma; Cl- = 89.3 ± 3.1 vs 97.0 ± 1.4 mEq/l plasma; OC = 281 ± 4.8 vs 300.2 ± 1.8 mOsm/kg plasma, respectively). In contrast, tissue Na+ and Cl- (mEq/100 g tissue) during Oe and Di did not differ (Na+ = 7.8 ± 0.8 vs 7.7 ± 0.9; Cl- = 7.6 ± 0.5 vs 7.8 ± 0.5, respectively). © 1990.