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Acute reduction of TxA2 platelet binding sites after in vivo administration of a TxA2 receptor inhibitor.
Author(s) -
Modesti PA,
Colella A.,
Cecioni I.,
Gensini GF,
Abbate R.,
Neri Serneri GG
Publication year - 1991
Publication title -
british journal of clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.216
H-Index - 146
eISSN - 1365-2125
pISSN - 0306-5251
DOI - 10.1111/j.1365-2125.1991.tb05560.x
Subject(s) - thromboxane a2 , platelet , receptor , medicine , endocrinology , pharmacology , placebo , population , chemistry , pathology , environmental health , alternative medicine
1. Picotamide has been shown to interfere competitively with the thromboxane A2 (TxA2) platelet receptor. In the present study the effect of in vivo administration of picotamide on TxA2 human platelet receptors was investigated in 10 healthy subjects. 2. Picotamide (300 mg x 3 daily) or placebo were administered in a double‐blind, cross‐ over, placebo controlled study, each treatment lasting 1 week with a 2 week interval period. TxA2 receptors were investigated by a direct radioligand binding assay method employing [125I]‐PTA‐OH as labelled ligand. Platelet studies were performed on the first day of treatment immediately before and 2, 4 and 8 h after the ingestion of the drug. The effects of chronic administration were assessed on the seventh day. 3. Two and 4 h after the administration of picotamide 300 mg orally platelet TxA2 receptors were significantly reduced from 1366 +/‐ 237 to 957 +/‐ 221 (P less than 0.05) and 753 +/‐ 119 receptors/platelet (mean +/‐ s.d.) (P less than 0.03). After 8 h platelet receptor population was restored (1362 +/‐ 324, NS). The same pattern was observed after 7 days of treatment. Thus picotamide seems to induce a short lasting down regulation of platelet TxA2 receptors.