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 Willebrand's disease.

OBJECTIVE: To determine whether plasma von Willebrand factor (vWf) concentration changes during the estrous cycle and pregnancy in Doberman Pinschers with type-I von Willebrand's disease (vWd) and in mixed-breed dogs with normal vWf, and if so, whether alterations in vWf concentration are associated with changes in serum concentrations of reproductive hormones. ANIMALS: 5 sexually intact female Doberman Pinschers with type-I vWf and 8 sexually intact female mixed-breed dogs with normal vWf. PROCEDURE: Concentrations of plasma vWf and serum progesterone and estradiol-17 beta were measured during the estrous cycle of nonpregnant dogs and during pregnancy, parturition, and lactation. Serum concentrations of total triiodothyronine, total thyroxin, and free thyroxin were measured during pregnancy, parturition, and lactation. RESULTS: Von Willebrand factor concentration did not change during the estrous cycle, but during pregnancy, vWf concentration gradually increased. Peak concentrations were obtained at parturition and were 103 and 92% higher in mixed-breed dogs and dogs with type-I vWd, respectively, than were mean prepregnancy (anestrus) values. At parturition, total triiodothyronine concentration decreased from the prepregnancy value. The increase in vWf concentration during pregnancy was positively associated with changes in concentration of estradiol-17 beta and was negatively associated with changes in concentration of progesterone. CONCLUSIONS: The 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 factors because vWf concentration did not change during the estrous cycle of nonpregnant dogs despite increases in concentrations of estradiol-17 beta and progesterone.

Inheritance of von Willebrand factor deficiency in Doberman pinschers.

OBJECTIVE: To determine the inheritance of von Willebrand factor (vWF) deficiency in Doberman Pinschers. DESIGN: Prospective, observational study. ANIMALS: 26 adult Doberman Pinschers or mixed-breed dogs and 101 pups produced from 18 matings between adult dogs. PROCEDURE: Measurement of plasma vWF concentrations in parents and progeny. On the basis of plasma vWF concentrations, dogs were grouped as normal (75 to 160 U of vWF/dl), midrange (> or = 30 and < 75 U of vWF/dl), or low (< 30 U of vWF/dl). RESULTS: The percentile distribution of vWF concentrations was trimodal. Distribution between dogs with low and midrange plasma vWF concentrations changed sharply, whereas the change between dogs with midrange and normal plasma vWF concentrations was gradual. Three matings between dogs with low vWF concentrations produced 13 offspring, all with low vWF concentrations. Two matings between dogs with normal plasma vWF concentrations produced 14 offspring, all with normal vWF concentrations. Eight matings between dogs with normal and low plasma vWF concentrations produced 54 offspring 40 with midrange, 13 with normal, and 1 with low vWF concentrations. There were 5 matings of dogs with midrange plasma vWF concentrations to dogs with low, midrange, or high vWF concentrations. The results of all matings were consistent with a single gene defect where each normal allele produced half the total amount of vWF when both alleles are normal and each defective allele produced < 15 U of vWF/dl. CLINICAL IMPLICATIONS: Dogs with low plasma vWF concentrations may be homozygous for the defective allele, whereas dogs with midrange plasma vWF concentrations may be heterozygous. It can be difficult to distinguish normal homozygotes from heterozygotes if evaluation is based only on plasma vWF concentration.