Effects of cardiac overexpression of type 6 adenylyl cyclase affects on the response to chronic pressure overload

Document Type

Article

Publication Date

9-1-2010

Abstract

Adenylyl cyclase (AC) type 5 (AC5) and AC type 6 (AC6) are the two major AC isoforms in the heart. Cardiac overexpression of AC6 has been shown to be protective in response to several interventions. In this investigation, we examined the effects of chronic pressure overload in AC6 transgenic (TG) mice. In the absence of any stress, AC6 TG mice exhibited enhanced contractile function compared with their wild-type (WT) littermates, i.e., increased (P < 0.05) left ventricular (LV) ejection fraction (EF) (75 ± 0.9 vs. 71 ± 0.5%) and LV dP/dt (7,850 ± 526 vs. 6,374 ± 315 mmHg/s). Forskolin (25 μg·kg-1·min-1 for 5 min) increased LVEF more (P < 0.05) in AC6 TG mice (14.8 ± 1.0%) than in WT mice (7.7 ± 1.0%). Also, isoproterenol (0.04 μg·kg -1·min-1 for 5 min) increased LVEF more (P < 0.05) in AC6 TG mice (18.0 ± 1.2%) than in WT mice (11.6 ± 2.1%). Pressure overload, induced by 4 wk of transverse aortic constriction (TAC), increased the LV weight-to-body weight ratio and myocyte cross-sectional area similarly in both groups, but reduced LVEF more in AC6 TG mice (22%) compared with WT mice (9%), despite the higher starting level of LVEF in AC6 TG mice. LV systolic wall stress increased more in AC6 TG mice than in WT mice, which could be responsible for the reduced LVEF in AC6 TG mice with chronic pressure overload. In addition, LV dP/dt was no longer elevated in AC6 TG mice after TAC compared with WT mice. LV end-diastolic diameter was also greater (P < 0.05) in AC6 TG mice (3.8 ± 0.07 mm) than in WT mice (3.6 ± 0.05 mm) after TAC. Thus, in contrast to other interventions previously reported to be salutary with cardiac AC6 overpression, the response to chronic pressure overload was not; actually, AC6 TG mice fared worse than WT mice. The mechanism may be due to the increased LV systolic wall stress in AC6 TG mice with chronic pressure overload. Copyright © 2010 the American Physiological Society.

Identifier

77955702308 (Scopus)

Publication Title

American Journal of Physiology Heart and Circulatory Physiology

External Full Text Location

https://doi.org/10.1152/ajpheart.00148.2010

e-ISSN

15221539

ISSN

03636135

PubMed ID

20562336

First Page

H707

Last Page

H712

Issue

3

Volume

299

Grant

P01AG027211

Fund Ref

National Institute on Aging

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