Contractile reserve but not tension is reduced in monocrotaline-induced right ventricular hypertrophy

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 55; no. 3; pp. H979 - H984
• Main Authors: VERSLUIS, J. Pieter, HESLINGA, Johannes W, SIPKEMA, Pieter, WESTERHOF, Nico
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Physiological Society 01.03.2004
• Subjects: Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Heart; Hypertension; Muscular system; Pulmonary arteries; Rodents; Vertebrates: cardiovascular system; sarcoplasmic reticulum function; intracellular ions; Vertebrata; Mammalia; Calcium; Sarcoplasmic reticulum; Circulatory system; Intracellular; 4,4'- diisothiocyanostilbene-2,2'-disulfonic acid; Inorganic element; Hypertrophy
• ISSN: 0363-6135; 1522-1539

The objective of this study was to evaluate the role of right ventricular hypertrophy on developed tension (Fdev) and contractile reserve of rat papillary muscle by using a model of monocrotaline (Mct)-induced pulmonary hypertension. Calcium handling and the influence of bicarbonate (symbol omitted) were also addressed with the use of two different buffers ([symbol omitted] and HEPES). Wistar rats were injected with either Mct (40 mg/kg sc) or vehicle control (Con). Isometrically contracting right ventricular papillary muscles were studied at 80% of the length of maximal developed force. Contractile reserve (1 - Fdev/Fmax) was calculated from Fdev and maximal tension (Fmax). Calcium recirculation was determined with postextrasystolic potentiation. Both groups of muscles were superfused with either (symbol omitted) (Con-B and Mct-B, both n = 6) or HEPES (Con-H and Mct-H, both n = 6) buffer. With hypertrophy, contractions were slower but Fdev was not changed. However, Fmax was decreased (P < 0.05). With (symbol omitted), Fmax decreased from 23.8 +/- 6.5 mN x mm-2 in Con-B, to 13.7 +/- 3.3 mN x mm-2 in Mct-B. With HEPES, it decreased from 16.3 +/- 3.5 mN x mm-2 (n = 6, Con-H) to 8.3 +/- 1.6 mN x mm-2 (Mct-H). Contractile reserve during hypertrophy was therefore also decreased (P < 0.05). With (symbol omitted), it decreased from 0.73 +/- 0.03 (Con-B) to 0.55 +/- 0.04 (Mct-B). With HEPES, it decreased (P < 0.001) from 0.64 +/- 0.07 (Con-H) to 0.19 +/- 0.06 (Mct-H). The recirculation fraction decreased (P < 0.05) from 0.59 +/- 0.04 in Con-B to 0.44 +/- 0.04 in Mct-B. We conclude that contractile reserve and recirculation fraction are impaired during hypertrophy, with a stronger effect under HEPES than (formula omitted) superfusion. [PUBLICATION ABSTRACT]