In:
American Journal of Physiology-Cell Physiology, American Physiological Society, Vol. 294, No. 6 ( 2008-06), p. C1566-C1575
Abstract:
Studies have shown that neuronal nitric oxide synthase (nNOS, NOS1) knockout mice (NOS1 −/− ) have increased or decreased contractility, but consistently have found a slowed rate of intracellular Ca 2+ ([Ca 2+ ] i ) decline and relengthening. Contraction and [Ca 2+ ] i decline are determined by many factors, one of which is phospholamban (PLB). The purpose of this study is to determine the involvement of PLB in the NOS1-mediated effects. Force-frequency experiments were performed in trabeculae isolated from NOS1 −/− and wild-type (WT) mice. We also simultaneously measured Ca 2+ transients (Fluo-4) and cell shortening (edge detection) in myocytes isolated from WT, NOS1 −/− , and PLB −/− mice. NOS1 −/− trabeculae had a blunted force-frequency response and prolonged relaxation. We observed similar effects in myocytes with NOS1 knockout or specific NOS1 inhibition with S-methyl-l-thiocitrulline (SMLT) in WT myocytes (i.e., decreased Ca 2+ transient and cell shortening amplitudes and prolonged decline of [Ca 2+ ] i ). Alternatively, NOS1 inhibition with SMLT in PLB −/− myocytes had no effect. Acute inhibition of NOS1 with SMLT in WT myocytes also decreased basal PLB serine16 phosphorylation. Furthermore, there was a decreased SR Ca 2+ load with NOS1 knockout or inhibition, which is consistent with the negative contractile effects. Perfusion with FeTPPS (peroxynitrite decomposition catalyst) mimicked the effects of NOS1 knockout or inhibition. β-Adrenergic stimulation restored the slowed [Ca 2+ ] i decline in NOS1 −/− myocytes, but a blunted contraction remained, suggesting additional protein target(s). In summary, NOS1 inhibition or knockout leads to decreased contraction and slowed [Ca 2+ ] i decline, and this effect is absent in PLB −/− myocytes. Thus NOS1 signaling modulates PLB serine16 phosphorylation, in part, via peroxynitrite.
Type of Medium:
Online Resource
ISSN:
0363-6143
,
1522-1563
DOI:
10.1152/ajpcell.00367.2007
Language:
English
Publisher:
American Physiological Society
Publication Date:
2008
detail.hit.zdb_id:
1477334-X
SSG:
12
Permalink