Role of. beta. -adrenoceptors in thyroxine-induced hypertrophy
The role of ..beta..-adrenoceptors in the development of thyroxine (T/sub 4/)-induced hypertrophy was studied in New Zealand white rabbits. Radiolabelled microspheres were used to measure coronary blood flow, and (/sup 125/I)-pindolol was used for Scatchard analysis of cardiac membranes to determine ..beta..-adrenoceptor density (B/sub max/) and affinity. After 16 d of T/sub 4/, coronary blood flow (CBF) was elevated from 257 +/- 31 ml/min/100 g (mean +/- SD) to 530 +/- 152 and B/sub max/ increased from 24.0 +/- 6.2 fmol/mg membrane protein to 47.3 +/- 12.0. Heart weight (HW) was elevated 30%, and heart weight/body weight (HW/BW) increased 70% above control. T/sub 4/ + propranolol (9 mg/kg/d) diminished CBF from levels seen with T/sub 4/ alone, to 361 +/- 146 ml/min/100g. However B/sub max/ elevations were unchanged from values with T/sub 4/. HW and HW/BW increases were insignificantly less than with T/sub 4/ alone. CBF in T/sub 4/ + pindolol (0.9 mg/kg/d) animals was similar to that with T/sub 4/ alone, but B/sub max/ increases were prevented (32.0 +/- 11.0). HW and HW/BW were both lower than with T/sub 4/ alone (153% of control). Thus, it appears that pindolol is more able to reverse some of the effects of T/sub 4/ than is propranolol, possibly due to prevention of ..beta..-adrenoceptor upregulation as a result of its intrinsic sympathomimetic ability.
- Research Organization:
- UMDNJ-Rutgers Medical School, Piscataway
- OSTI ID:
- 7189480
- Report Number(s):
- CONF-8604222-
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 45:4; Conference: 70. annual meeting of the Federation of American Society for Experimental Biology, St. Louis, MO, USA, 13 Apr 1986
- Country of Publication:
- United States
- Language:
- English
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550201* - Biochemistry- Tracer Techniques