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Inhibition of human platelet adenylate cyclase by collagen fibres. Effect of collagen is additive with that of adrenaline, but interactive with that of thrombin.

ABSTRACT: Collagen fibres in suspension have been shown to inhibit adenylate cyclase in human platelet preparations. Direct inhibition by collagen fibres was observed when intact platelets were used, although secondary events such as ADP secretion or prostanoid formation were important contributors to the inhibition of adenylate cyclase after treatment of platelets with collagen. The nature of the direct inhibition caused by collagen has been investigated in platelet membrane preparations, with the following results. (1) Collagen fibres inhibit platelet membrane adenylate cyclase in a dose-dependent manner. (2) Inhibition of adenylate cyclase by thrombin, adrenaline or collagen fibres could be abolished in the presence of guanosine 5'-[beta-thio]diphosphate; half-maximal inhibition was obtained at about 100 microM for the inhibitory action of thrombin, and at about 500 microM for that of either adrenaline or collagen. (3) The action of each ligand was blocked to a similar extent by pertussis-toxin treatment of the platelet membranes. Taken together, these results indicate that the action of collagen, like that of thrombin and adrenaline, is G-protein-dependent. (4) inhibition of adenylate cyclase by collagen fibres was additive with that caused by adrenaline, but co-operative with that caused by thrombin, suggesting that inhibitory pathways exists for collagen and adrenaline which are distinct from, but interactive with, that for thrombin. (5) Modification of the collagen fibres by pepsin treatment attenuated the effects of collagen, whereas heat-denaturation of the collagen fibres completely abolished their effects. These data suggest that the effects of collagen are specific, and depend on the detailed structure of the collagen fibres.

SUBMITTER: Farndale RW

PROVIDER: S-EPMC1130885 | biostudies-other | 1992 Feb

REPOSITORIES: biostudies-other

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Project description:BackgroundTotal hip arthroplasty (THA) can be associated with substantial peri-operative blood loss which can negatively influence a patient's clinical outcome. Few haemostatic agents have been tested in THA. The aim of this study was to determine whether the use of a collagen/thrombin/ autologous platelet haemostatic agent would result in a significant decrease of blood transfusions for patients undergoing primary THA.Materials and methodsTHA patients meeting inclusion/exclusion criteria (n=109) were enrolled in this prospective, double-blind trial and randomised to a treatment arm (standard haemostatic methods plus haemostatic agent) or control arm (standard haemostatic methods only). The primary outcome was transfusion. Secondary outcome measures included peri-operative narcotic usage and post-operative haemoglobin levels, pain scores, function, and general health quality of life.ResultsTransfusions were required by 5/60 (8.3%) patients in the treatment group and 7/49 (14.3%) in the control group (p=0.33). The mean number of units transfused was not significantly different between the treatment group (2.2±1.3) and the control group (1.6±0.5) (p=0.36). Haemoglobin values on post-operative days 1, 2, and 3 were significantly higher in the treatment group (p=0.002, 0.04, and 0.02, respectively). Hip Disability and Osteoarthritis Outcome Score and Short Form-12 scores were not different between the two groups.DiscussionIn relatively healthy patients undergoing primary cementless THA there was no significant difference in number of transfusions or number of units transfused. It is unlikely that we will routinely use the investigated haemostatic agent to reduce blood loss in a healthy patient undergoing THA. The product may have some benefit in patients who refuse blood transfusions, have minimal ability to increase blood volume, are undergoing total joint revision, or have markedly low pre-operative haemoglobin levels, but this needs to be demonstrated.

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Inhibition of human platelet adenylate cyclase by collagen fibres. Effect of collagen is additive with that of adrenaline, but interactive with that of thrombin.

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