Northern elephant seal platelets: Analysis of shape change and response to platelet agonists

Cara L. Field, Naomi J. Walker, Fern Tablin

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

Blood platelets have a vital role in the maintenance of normal mammalian hemostasis. Rapid pressure changes and temperatures lower than 20°C cause activation of human and terrestrial mammal platelets. Elephant seals are routinely subjected to pressures as high as 150 atm, yet do not suffer from the thrombotic effects of platelet activation associated with rapid decompression. We examined the ultrastructure of Northern elephant seal (Mirounga angustirostris) platelets and their functional and morphological response to various platelet agonists. Unstimulated elephant seal platelets are discoid cells, with a microtubule coil, randomly dispersed alpha and dense granules, and glycogen granules. There are well-defined areas of membranous invaginations that indicate the presence of an open canalicular system (OCS). Aggregometry was used to determine the response of elephant seal platelets to various platelet agonists. Dose-dependent curves were generated for thrombin, collagen, and adenosine diphosphate (ADP). Platelet response to thrombin was dose-dependent and was maximal at 2.5 U/ml. Platelets collected in sodium citrate had blunted responses to both ADP and collagen. ADP stimulation caused only reversible, primary activation (shape change) at ≥5 μM, while platelets did not aggregate in response to any concentration of collagen. Platelets collected in sodium heparin did respond fully to both to ADP and collagen. There was small, reversible shape change in response to ristocetin, but no response to epinephrine. Decreased sensitivity of elephant seal platelets to agonists may be a protective mechanism developed in response to rapid pressure changes and cold temperatures associated with adaptation to an extreme environment.

Original languageEnglish (US)
Pages (from-to)267-277
Number of pages11
JournalThrombosis Research
Volume101
Issue number4
DOIs
StatePublished - Feb 15 2001

Keywords

  • Aggregation
  • Collagen
  • Elephant seals
  • Platelet agonists
  • Platelets

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Hematology

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