RESUMO
We investigated the platelet aggregation inhibiting activity of human placental brush border membrane vesicles (BBMV) and obtained the following results. A strong platelet aggregation inhibiting activity existed in placental BBMV. The BBMV inhibited the platelet aggregation induced by ADP, arachidonic acid, collagen and ristocetin in a dose-dependent manner. The protein concentration of BBMV giving 50 per cent inhibition was 52 +/- 6 micrograms/ml for ADP-induced platelet aggregation, 21 +/- 2 micrograms/ml for arachidonic acid-induced platelet aggregation, 19 +/- 2 micrograms/ml for collagen-induced platelet aggregation and 107 +/- 9 micrograms/ml for ristocetin-induced platelet aggregation. There was a high level of ADP degrading activity (ADPase activity) in the placental BBMV. ADP degrading activity of the BBMV: 10.5 +/- 0.5 mumol/mg protein/min was 21 times greater than that of homogenate of the placental villi. The placental BBMV inhibited platelet TXA2 production. In the 40 micrograms/ml protein concentration of placental BBMV, platelet TXA2 production was almost completely inhibited.
Assuntos
Vilosidades Coriônicas/fisiologia , Agregação Plaquetária/fisiologia , Difosfato de Adenosina/metabolismo , Difosfato de Adenosina/farmacologia , Ácido Araquidônico/farmacologia , Plaquetas/metabolismo , Colágeno/farmacologia , Epoprostenol/biossíntese , Feminino , Humanos , Agregação Plaquetária/efeitos dos fármacos , Gravidez , Terceiro Trimestre da Gravidez/fisiologia , Ristocetina/farmacologia , Tromboxano A2/biossínteseRESUMO
In a 71-year-old woman with primary squamous cell carcinoma of the thyroid, marked leukocytosis (26,000 to 87,000/mm3), in which about 90% were mature neutrophils, was observed. Hypercalcemia (about 12 mg/100 ml) was also observed with the serum inorganic phosphate within normal limits. The serum parathyroid hormone (PTH) was undetectable. The thyroid tumor was successfully transplanted to athymic nude mice at autopsy. Marked leukocytosis and hypercalcemia was reproduced in the tumor-bearing nude mice. The result indicates that the thyroid cancer was secreting humoral factors(s) producing leukocytosis and hypercalcemia. The association of leukocytosis and hypercalcemia has been reported in the two similar cases of squamous cell carcinoma, in which the tumor was proven to secrete colony-stimulating factor (CSF). Leukocytosis and hypercalcemia may thus form a new paraneoplastic syndrome.
