Selective ETB1 stimulation relaxes the iris sphincter muscle.

• Type: Summary of Presentation in an International Conference
• Date: 2004

Authors

Rocha-Sousa A (Author) FMUP; Saraiva I (Author) Other; Falcão-Reis F (Author) FMUP; Leite Moreira AF (Author) FMUP

Conference proceedings International

Title: Ophthalmic Research

Initial page: 145

European Association for Vision and Eye research (EVER).

Vilamoura, Portugal, 24 27 de Setembro de 2004

Scientific classification

FOS: Medical and Health sciences > Other medical sciences

Other information

Resumo (PT): Purpose: Endothelin–1 (ET-1) effects are mediated by two different receptors (ETA and ETB). The later include ETB1 (endothelial) and ETB2 (muscular) subtypes. ETB1 stimulation promotes NO release and Pg production. The present study investigated, in rabbit iris sphincter muscles, the effects of selective ETB stimulation. Methods: Rabbit iris sphincter muscles (n=46) were dissected and attached to a force transducer, on a vertical organ bath containing a modified Krebs-Ringer solution (1.8 mM Ca2+; 35ºC).The effects of ETB stimulation by Sarafotoxin (SRTX; 2*10e-7 M) were studied alone (n=10) or in presence of: (i) a selective ETA receptor antagonist, (BQ-123; 10e-5 M ; n=7); (ii) a selective ETB2 antagonist, (BQ 788; 10e-5 M; n=7); (iii) a NOS inhibitor (LNA; 10e-4 M; n=7) (iv) and a COX inhibitor (Indomethacin; 10e-5 M; n=7). Finally the effects of a selective ETB1 agonist (IRL-1620 10e-6 M; n=8) were evaluated. All effects were recorded and analysed after an isometric contraction elicited by Carbachol (10e-4 M). Only significant results (mean±SE, p<0.05) are given, expressed as % changes from control. Results: When compared to control, SRTX promoted a 4,8±1,6% decrease in isometric tension, 2’ 30’’ after its addition to the bathing solution, an effect that disappeared at 10’. This effect was not affected by BQ-788 (tension decreased 4.0±1.7%), BQ-123 (4.3±0.8%) or L-NA (5.6±1.5%), but was slightly but not significantly attenuated by INDO (3.5±0.9%); yet it was increased by selective ETB1 stimulation with IRL-1620 (tension decreased 6.9±1.6%). Conclusions: ETB stimulation relaxes the iris sphincter muscle, an effect that seems to be mediated by the ETB1 subtype.

Language: English

Type (Professor's evaluation): Scientific

Notes: European Association for Vision and Eye research (EVER), published in journal, Ophthalmic Research. 2004; 36(Suppl.1):145.