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Biomedical Research

Changes of P2X-purinoceptors in rat vas deferens and spleen caused by long term guanethidine treatment

Author(s): M. Zhao, P. Milner

Vol. 14, No. 1 (2003-01 - 2003-06)

Correspondence to:

Dr. M. Zhao
Department Biomedical Sciences
University of Aberdeen
Aberdeen AB25 2ZD
United Kingdom

Phone: +44 1224 555732
Fax: + 44 1224 555719
e-mail: m.zhao(at)abdn.ac.uk

Using [3H] a, b-Methylene ATP ([3H] a, b-MeATP) as the radioligand, changes in the P2X-purinoceptor density and affinity in rat vas deferens and spleen have been examined following long-term guanethidine treatment. Large doses of guanethidine (50mg/kg) were given daily for 3 weeks to 8-day-old rat pups, which were killed at 14 weeks of age. The results showed that in guanethidine-treated rats P2X-purinoceptor densities (Bmax) of both the high and low affinity components were significantly increased (P<0.05). The Bmax for the high affinity site were increased significantly (P<0.05): from 1.0±0.2 to 3.4±0.8 (pmol/mg.protein) in the spleen, from 3.2±0.7 to 22.3±4.3 in the vas deferens, while the affinity was decreased as shown by Kd from 5.4±1.0 to 18.1±2.5 nM in the spleen and from 1.2±0.3 to 5.4±2.2 nM in the vas deferens (P<0.01) after guanethidine treatment. The Bmax for the low affinity site were also increased significantly (P<0.05) from 16.0±3.6 to 160.0±10.6 (pmol/mg.protein) in the spleen, from 9.7±2.0 to 296.4±52.5 in the vas deferens, while the affinity was decreased as shown by Kd from 222±57 to 882±298 nM (P=0.08) in the spleen and from 11.3±4.2 to 122.7±24.2 nM in the vas deferens (P<0.05) after guanethidine treatment. It is concluded that following sympathectomy and loss of the cotransmitter ATP in the vas deferens and spleen, there is an increase in density of P2X receptor sites, although a decrease in receptor affinity.

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