ABSTRACT
The fraction of free fatty acids (FFA) is present in skeletal muscles. However, there is almost no data regarding regulation in the content of this intramuscular lipid pool. We took advantage of the isolated muscle preparation to examine whether: a) increasing exogenous concentration of FFA (500microM or 700microM, 30min) b) insulin (10.00 I.U./L, 30min), c) adrenalin (4.4 nM, 30 min), or d) contractions (200ms, tetani, 1Hz, 30min), affect the FFA content inside myocytes. Incubation of soleus (S) and extensor digitorum longus (EDL) with increasing concentrations of exogenous FFA (from 500microM to 700microM) resulted in an increase in the total FFA fraction in both muscles studied (by 280.2% and 259.1%, respectively). In contracting muscles FFA pool was significantly reduced both in S (by 73.1%) and in EDL (by 31.1%). Neither stimulation by adrenalin nor insulin affected the total content of FFA fraction in the muscles examined. We conclude that a) increased availability of exogenous FFA at the sarcolemma level results in an increase in the size of intramuscular FFA fraction b) the intracellular FFA fraction is utilized by contracting muscles with regard to the fiber composition and to a greater extent in more oxidative muscles, c) FFA fraction remains stable upon stimulation by insulin or adrenalin.
Subject(s)
Epinephrine/pharmacology , Fatty Acids, Nonesterified/metabolism , Hypoglycemic Agents/pharmacology , Insulin/pharmacology , Muscle Contraction/physiology , Muscle, Skeletal/metabolism , Vasoconstrictor Agents/pharmacology , Animals , In Vitro Techniques , Male , Muscle, Skeletal/drug effects , Muscle, Skeletal/physiology , Rats , Rats, WistarABSTRACT
AIM: Hormone-sensitive lipase (HSL) has been proposed to regulate triacylglycerol (TG) breakdown in skeletal muscle. In muscles with different fibre type compositions the influence on HSL of two major stimuli causing TG mobilization was studied. METHODS: Incubated soleus and extensor digitorum longus (EDL) muscles from 70 g rats were stimulated by adrenaline (5.5 microm, 6 min) or contractions (200 ms tetani, 1 Hz, 1 min) in maximally effective doses or by both adrenaline and contractions. RESULTS: Hormone-sensitive lipase activity was increased significantly by adrenaline as well as contractions, and the highest activity (P < 0.05) was seen with combined stimulation [Soleus: 0.40 +/- 0.03 (SE) m-unit mg protein(-1) (basal), 0.65 +/- 0.02 (adrenaline), 0.65 +/- 0.03 (contractions), 0.78 +/- 0.03 (adrenaline and contractions); EDL: 0.18 +/- 0.01, 0.30 +/- 0.02, 0.26 +/- 0.02, 0.32 +/- 0.01]. Glycogen phosphorylase activity was always increased more by adrenaline compared with contractions [Soleus: 60 +/- 4 (a/a + b)% vs. 46 +/- 3 (P < 0.05); EDL: 60 +/- 5 vs. 39 +/- 6 (P < 0.05)]. After combined stimulation glycogen phosphorylase activity in soleus [59 +/- 3 (a/a + b)%] was identical to and in EDL [45 +/- 4 (a/a + b)%] smaller (P < 0.05) than the activity after adrenaline only. CONCLUSIONS: In slow-twitch oxidative as well as in fast-twitch glycolytic muscle HSL is activated by both adrenaline and contractions. These stimuli are partially additive indicating at least partly different mechanisms of action. Contractions may impair the enhancing effect of adrenaline on glycogen phosphorylase activity in muscle.
Subject(s)
Epinephrine/pharmacology , Glycogen Phosphorylase/metabolism , Muscle Contraction/physiology , Muscle, Skeletal/enzymology , Sterol Esterase/metabolism , Animals , Electric Stimulation , Epinephrine/analysis , Lactates/analysis , Male , Muscle Fibers, Skeletal/drug effects , Muscle Fibers, Skeletal/enzymology , Muscle, Skeletal/drug effects , Muscle, Skeletal/physiology , Rats , Rats, Wistar , Triglycerides/metabolismABSTRACT
Alanine aminotransferase (AlAT), aspartate aminotransferase (AspAT), adenosine deaminase (ADA) and 5'-nucleotidase (5'-NT) activities were studied in the rat intestine smooth muscles after 24 and 48 hours of fasting. It was found that fasting evoked a significant decrease in ADA and increase in 5'-NT activities in all intestinal segments analysed. A dual effect of fasting was noted for AspAT and AlAT; after first 24h of fasting the activities of both enzymes decreased and increased again when fasting was continued to 48h. We conclude that during fasting an adaptive response occurs in the smooth muscles of intestine and this may be a part of systemic adaptation to fasting.
Subject(s)
Fasting/physiology , Intestines/enzymology , Muscle, Smooth/enzymology , 5'-Nucleotidase/metabolism , Adaptation, Physiological , Adenosine Deaminase/metabolism , Alanine Transaminase/metabolism , Animals , Aspartate Aminotransferases/metabolism , Male , Rats , Rats, WistarABSTRACT
Adenosine deaminase activity was studied in the gastric mucosa of patients with peptic ulcer in relation to ulcer localisation and treatment with ranitidine or sucralfate. Enzyme activities observed in the corpus mucosa were higher at a distance of over 2 cm from the ulcer margin than that recorded close to the ulcer. A significant decrease in adenosine deaminase activity was found after treatment with ranitidine but not with sucralfate. In the antral mucosa, enzyme activity was constant in all the groups observed. The evaluation of adenosine deaminase activity in gastric mucosa can be useful for studies of pathologic changes in the stomach.
