The effect on circulating platelet count of repeated intravenous infusions of collagen fibrils was measured in male OFA Sprague-Dawley rats (400-550 g). Citrated blood was pumped from the left carotid artery of anaesthetized animals, via a siliconized double-lumen cannula, into the manifold of a Technicon Autocounter, for continuous registration of platelet count. Native collagen fibrils (Collagenreagent ‘Horm’) were infused intravenously for 1 min at 15 min intervals. Successive increasing collagen doses (20-320 pg/kg) induced dose-dependent reduction in platelet count, measured as absolute platelet number disappearing from the circulation. Repeated infusion of collagen 160 pg/kg produced constant, partially reversible, reduction in platelet count. Several known inhibitors of platelet aggregation were investigated in the described test system. Collagen effects were inhibited in a dose-dependent manner to a maximum of 50-60 %, and drug activity was thus quantitated on the basis of dose producing 30 % inhibition (ID30): prostaglandin E1 (1.6 pg/kg/min i.v. infusion), SH-869 (1.1 mg/kg i.v.), aspirin (33.1 mg/kg p.o.), proquazone, a new non-steroidal antiinflammatory compound (5.0 mg/kg p.o.). That part of the collagen response not inhibited might be attributed to the initial phase of platelet adhesion to collagen, known to be relatively refractive to platelet function inhibitors.
In Utero Exposure to Di(n)butyl Phthalate Reduces Testicular Testosterone and Testes Size in a Dose-Dependent Manner in Harlan Sprague Dawley Fetal Rats.
