Hardie. Effects of endurance training on activity and expression of AMP-activated protein kinase isoforms in rat muscles. Am J Physiol Endocrinol Metab 283: E178-E186, 2002. First published March 12, 2002 10.1152/ajpendo.00404.2001.-The effects of endurance training on the response of muscle AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC) to moderate treadmill exercise were examined. In red quadriceps, there was a large activation of ␣2-AMPK and inactivation of ACC in response to exercise. This response was greatly reduced after training, probably because of reduced metabolic stress. In white quadriceps, there were no effects of exercise on AMPK or ACC, but ␣2-activity was higher after training because of increased phosphorylation of Thr 172 . In soleus, there were small increases in ␣2-activity during exercise that were not affected by training. The expression of all seven AMPK subunit isoforms was also examined. The ␤2-and ␥2-isoforms were most highly expressed in white quadriceps, and ␥3 was expressed in red quadriceps and soleus. There was a threefold increase in expression of ␥3 after training in red quadriceps only. Our results suggest that ␥3 might have a special role in the adaptation to endurance exercise in muscles utilizing oxidative metabolism.

. Ca 2ϩ channel subtypes expressed by dopaminergic (DA) neurons in the substantia nigra pars compacta (SNc) were studied using whole cell patch-clamp recordings and blockers selective for different channel types (L, N, and P/Q). Nimodipine (Nim, 2 M), -conotoxin GVIA (Ctx, 1 M), or -agatoxin IVA (Atx, 50 nM) blocked 27, 36, and 37% of peak whole cell Ca 2ϩ channel current, respectively, indicating the presence of L-, N-, and P-type channels. Nim blocked approximately twice as much Ca 2ϩ channel current near activation threshold compared with Ctx or Atx, suggesting that small depolarizations preferentially opened L-type versus N-or P-type Ca 2ϩ channels. N-and L-channels in DA neurons opened over a significantly more negative voltage range than those in rat dorsal root ganglion cells, recorded from using identical conditions. These data provide an explanation as to why Ca 2ϩ -dependent spontaneous oscillatory potentials and rhythmic firing in DA neurons are blocked by L-channel but not N-channel antagonists and suggest that pharmacologically similar Ca 2ϩ channels may exhibit different thresholds for activation in different types of neurons. I N T R O D U C T I O NNumerous studies have indicated that Ca 2ϩ entry is important in regulating the firing patterns of dopaminergic (DA) neurons in the substantia nigra. The pacemaker-like slow depolarizations (PLSD), spontaneous oscillatory potentials (SOPs), and slow afterhyperpolarizations involved in regulation of DA neuron firing activity have all been shown to be Ca 2ϩ dependent (Fujimura and Matsuda 1989; Grace and Onn 1989; Harris et al. 1989; Kang and Kitai 1993a,b; Mercuri et al. 1994; Nedergaard et al. 1993; Ping and Shepard 1996; Yung et al. 1991). A previous study suggests that DA neurons express L-, N-, P/Q-, and R-type Ca 2ϩ channels (Cardozo and Bean 1995). However, the Ca 2ϩ channel subtype(s) involved in regulation of DA neuron firing behavior have not been conclusively determined. In two studies, DA neuron spontaneous firing and SOPs were abolished by dihydropyridines but not -conotoxin GVIA (Ctx), suggesting a prominent role for L-, but not N-type Ca 2ϩ channels in these phenomena (Mercuri et al. 1994; Nedergaard et al. 1993). However, Kang and Kitai (1993b) provided evidence that DA neuron pacemaker activity was underlain by N-but not L-type Ca 2ϩ channels. Finally, a study by Fujimura and Matsuda (1989) suggested that neither N-nor L-channels were involved in DA neuron pacemaker activity.The present study investigated the relative contribution of L-, N-, and P-type Ca 2ϩ channels to whole cell Ca 2ϩ channel current at different membrane potentials, to see which of the three channels opened at membrane potentials that would be commensurate with a role in the PLSD. We also compared the voltage dependence of DA neuron Ca 2ϩ channel activation to that of dorsal root ganglion (DRG) neurons. Our data indicate that a larger proportion of the whole cell Ca 2ϩ current observed near activation threshold is conducted through L-channels versus N-or P-chann...

In this work, we aimed to study the effect of uric acid on gentamicin-induced nephrotoxicity. Male Sprague-Dawley rats were assigned to one of six groups (six rats each) which received intraperitoneal injections for 9 days: (S) saline; (UA) Uric acid alone; (G) Gentamicin alone; (G + UA) Gentamicin + uric acid; (G rec) Gentamicin recovery and (G + UA rec) Gentamicin + uric acid recovery. In (G rec) and (G + UA rec), rats recovered for 7 days after the last injection. Urine and blood samples were taken on day 0 and at the end of every stage. Kidneys were harvested for histological scoring, determination of renal malondialdehyde (MDA), zymography and western blots for matrix metalloprotease (MMP)-2 and MMP-9. Uric acid alone did not provoke changes in biochemical and histological parameters when compared to controls. Gentamicin alone increased significantly plasma creatinine and blood urea nitrogen and caused a moderate histological damage. When combined with uric acid, these conditions worsened. MMP-9 activity and expression was decreased in rats from group G + UA as compared with rats from group G, while activity of MMP-2 was similarly increased in both groups when compared to controls. The increase in renal MDA induced by gentamicin was not altered when it was combined with uric acid. During the recovery stage, all biochemical parameters returned to normal levels, though a trend for delay of tubular damage recovery was observed in group G + UA rec when compared with group G rec. The results indicate that uric acid worsens gentamicin-induced nephrotoxicity. The mechanism is likely to implicate down-regulation of MMP-9.

Fructose 2,6-bisphosphate is a potent endogenous stimulator of glycolysis. A high aerobic glycolytic rate often correlates with increased cell proliferation. To investigate this relationship, we have produced clonal cell lines of Rat-1 fibroblasts that stably express transgenes coding for 6-phosphofructo-2-kinase, which catalyzes the synthesis of fructose 2,6-bisphosphate, or for fructose 2,6-bisphosphatase, which catalyzes its degradation. While serum deprivation in culture reduced the growth rate of control cells, it caused apoptosis in cells overproducing fructose 2,6-bisphosphate. Apoptosis was inhibited by 5-amino-4-imidazolecarboxamide riboside, suggesting that 5P-AMP-activated protein kinase interferes with this phenomenon.z 1999 Federation of European Biochemical Societies.