POSTIMPLANTATION INCREASE IN PLASMA-FIBRINOGEN CONCENTRATION WITH INCREASE IN RELAXIN CONCENTRATION IN PREGNANT DOGS

Objective-To determine time courses of pregnancy-related changes in pl asma fibrinogen, serum relaxin, and serum C-reactive protein-like immu noreactivity (CRP-LI) concentrations in pregnant and nonpregnant dogs. Animals-16 pregnant and 13 nonpregnant Beagles, 6 pregnant Beagles, a nd 3 pregnant and 3 nonpregnant dogs of other breeds. Procedure-Fibrin ogen was measured by nephelometric centrifugal analysis of light scatt er in plasma samples of all dogs, and CRP-LI was measured by fluoresce nce immunoassay in selected sera from 10 pregnant and 10 nonpregnant d ogs, Relaxin was measured in selected sera from 7 pregnant and 7 nonpr egnant dogs. Results-During pregnancy, fibrinogen concentration increa sed between days 21 and 30 after the luteinizing hormone surge, and wa s > 280 mg/dl between days 29 and 50 in 84 of 86 samples, with peak va lues 539 +/- 29 mg/dl higher (P < 0.01) than those in nonpregnant dogs (188 +/- 8 mg/dl), higher values from days 21 to 50 (P < 0.01) than t hose in nonpregnant dogs, acid values similar to those in nonpregnant dogs after day 50. Relaxin concentration was increased from days 26 to 30 and 0 to 4 days after fibrinogen concentration increased in pregna nt dogs, and was not detectable in nonpregnant dogs. The CRP-LI concen tration was higher in pregnant dogs at days 26 to 50, but values were inconsistent within and among dogs, and near the limit of sensitivity of the assay. Conclusions-Concentration of the acute-phase reactant pr otein fibrinogen increases after day 20 following implantation in dogs , at or just before the pregnancy-specific increase in relaxin concent ation from days 26 to 30, and persists until day 50. Clinical Relevanc e-Fibrinogen assay may be useful for pregnancy diagnosis in dogs.