Abstract
Functional vicinal sulfhydryls are essential for insulin-stimulated system A neutral amino acid uptake in the rat epitrochlearis muscle. In skeletal muscle, system A uptake is also activated by contractile activity. Therefore, the purposes of this study were to characterize the stimulation of system A activity by contractions induced by electrical stimulation in vitro, and to assess the role of vicinal sulfhydryls in this process. System A activity in the isolated epitrochlearis muscle was measured using the nonmetabolizable analogue α-(methylamino)isobutyric acid (MeAIB). Contractions increased MeAIB uptake by increasing the apparent maximal velocity (Vmax), with no alteration in the apparent Km. The maximal stimulatory effects of insulin and contractions on MeAIB uptake were completely additive, demonstrating that these two stimuli exert their effects via different mechanisms. Phenylarsine oxide (PAO), a vicinal sulfhydryl antagonist, at greater than 20 μmol/L inhibited basal and contraction-stimulated MeAIB uptake by approximately 50% and 70%, respectively, by decreasing Vmax, with no change in Km. Both inhibitory effects were completely prevented by cotreatment with the vicinal dithiol dimercaptopropanol (DMP), indicating the effects were mediated by interactions with vicinal sulfhydryls. Contraction-stimulated MeAIB uptake was rapidly (half-time, ∼7 minutes) reversed by the addition of PAO. These results (1) define conditions under which contraction-stimulated system A amino acid uptake can be studied in an isolated mammalian skeletal muscle preparation, and (2) indicate that vicinal sulfhydryls are essential for stimulation of system A activity by muscle contractions.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 440-445 |
| Number of pages | 6 |
| Journal | Metabolism: Clinical and Experimental |
| Volume | 42 |
| Issue number | 4 |
| DOIs | |
| State | Published - 1993 |
Fingerprint
ASJC Scopus subject areas
- Endocrinology
- Endocrinology, Diabetes and Metabolism
Cite this
Regulation of contraction-stimulated system a amino acid uptake in skeletal muscle : Role of vicinal sulfhydryls. / Henriksen, Erik J; Schneider, Madeline C.; Ritter, Leslie S.
In: Metabolism: Clinical and Experimental, Vol. 42, No. 4, 1993, p. 440-445.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Regulation of contraction-stimulated system a amino acid uptake in skeletal muscle
T2 - Role of vicinal sulfhydryls
AU - Henriksen, Erik J
AU - Schneider, Madeline C.
AU - Ritter, Leslie S
PY - 1993
Y1 - 1993
N2 - Functional vicinal sulfhydryls are essential for insulin-stimulated system A neutral amino acid uptake in the rat epitrochlearis muscle. In skeletal muscle, system A uptake is also activated by contractile activity. Therefore, the purposes of this study were to characterize the stimulation of system A activity by contractions induced by electrical stimulation in vitro, and to assess the role of vicinal sulfhydryls in this process. System A activity in the isolated epitrochlearis muscle was measured using the nonmetabolizable analogue α-(methylamino)isobutyric acid (MeAIB). Contractions increased MeAIB uptake by increasing the apparent maximal velocity (Vmax), with no alteration in the apparent Km. The maximal stimulatory effects of insulin and contractions on MeAIB uptake were completely additive, demonstrating that these two stimuli exert their effects via different mechanisms. Phenylarsine oxide (PAO), a vicinal sulfhydryl antagonist, at greater than 20 μmol/L inhibited basal and contraction-stimulated MeAIB uptake by approximately 50% and 70%, respectively, by decreasing Vmax, with no change in Km. Both inhibitory effects were completely prevented by cotreatment with the vicinal dithiol dimercaptopropanol (DMP), indicating the effects were mediated by interactions with vicinal sulfhydryls. Contraction-stimulated MeAIB uptake was rapidly (half-time, ∼7 minutes) reversed by the addition of PAO. These results (1) define conditions under which contraction-stimulated system A amino acid uptake can be studied in an isolated mammalian skeletal muscle preparation, and (2) indicate that vicinal sulfhydryls are essential for stimulation of system A activity by muscle contractions.
AB - Functional vicinal sulfhydryls are essential for insulin-stimulated system A neutral amino acid uptake in the rat epitrochlearis muscle. In skeletal muscle, system A uptake is also activated by contractile activity. Therefore, the purposes of this study were to characterize the stimulation of system A activity by contractions induced by electrical stimulation in vitro, and to assess the role of vicinal sulfhydryls in this process. System A activity in the isolated epitrochlearis muscle was measured using the nonmetabolizable analogue α-(methylamino)isobutyric acid (MeAIB). Contractions increased MeAIB uptake by increasing the apparent maximal velocity (Vmax), with no alteration in the apparent Km. The maximal stimulatory effects of insulin and contractions on MeAIB uptake were completely additive, demonstrating that these two stimuli exert their effects via different mechanisms. Phenylarsine oxide (PAO), a vicinal sulfhydryl antagonist, at greater than 20 μmol/L inhibited basal and contraction-stimulated MeAIB uptake by approximately 50% and 70%, respectively, by decreasing Vmax, with no change in Km. Both inhibitory effects were completely prevented by cotreatment with the vicinal dithiol dimercaptopropanol (DMP), indicating the effects were mediated by interactions with vicinal sulfhydryls. Contraction-stimulated MeAIB uptake was rapidly (half-time, ∼7 minutes) reversed by the addition of PAO. These results (1) define conditions under which contraction-stimulated system A amino acid uptake can be studied in an isolated mammalian skeletal muscle preparation, and (2) indicate that vicinal sulfhydryls are essential for stimulation of system A activity by muscle contractions.
UR - http://www.scopus.com/inward/record.url?scp=0027481883&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0027481883&partnerID=8YFLogxK
U2 - 10.1016/0026-0495(93)90100-3
DO - 10.1016/0026-0495(93)90100-3
M3 - Article
VL - 42
SP - 440
EP - 445
JO - Metabolism: Clinical and Experimental
JF - Metabolism: Clinical and Experimental
SN - 0026-0495
IS - 4
ER -