PLASMA VON-WILLEBRAND-FACTOR CHANGES DURING VARIOUS REPRODUCTIVE-CYCLE STAGES IN MIXED-BREED DOGS WITH NORMAL VON-WILLEBRAND-FACTOR AND IN DOBERMAN-PINSCHERS WITH TYPE-I VON-WILLEBRANDS-DISEASE

Objective-To determine whether plasma von Willebrand factor (vWf) conc entration changes during the estrous cycle and pregnancy in Doberman P inschers with type-I von Willebrand's disease (vWd) and in mixed-breed dogs with normal vWf, and if so, whether alterations in vWf concentra tion are associated with changes in serum concentrations of reproducti ve hormones. Animals-5 sexually intact female Doberman Pinschers with type-I vWd and 8 sexually intact female mixed-breed dogs with normal v Wf. Procedure-Concentrations of plasma vWf and serum progesterone and estradiol-17 beta were measured during the estrous cycle of nonpregnan t dogs and during pregnancy, parturition, and lactation. Serum concent rations of total triiodothyronine, total thyroxin, and free thyroxin w ere measured during pregnancy, parturition, and lactation. Results-Von Willebrand factor concentration did not change during the estrous cyc le, but during pregnancy, vWf concentration gradually increased. Peak concentrations were obtained at parturition and were 103 and 92% highe r in mixed-breed dogs and dogs with type-I vWd, respectively, than wer e mean prepregnancy (anestrus) values. At parturition, total triiodoth yronine concentration decreased from the prepregnancy value. The incre ase in vWf concentration during pregnancy was positively associated wi th changes in concentration of estradiol-17 beta and was negatively as sociated with changes in concentration of progesterone. Conclusions-Th e increase in vWf concentration in pregnant bitches may be associated with changes in concentrations of reproductive hormones. However, the increase in vWf concentration during pregnancy may involve other facto rs because vWf concentration did not change during the estrous cycle o f nonpregnant dogs despite increases in concentrations of estradiol-17 beta and progesterone.