Histochemistry of sarcoplasmic reticulum Ca-ATPase using dysprosium as capturing reagent.
This report describes the development of a histochemical method for the demonstration of sarcoplasmic reticulum Ca-ATPase activity in cross-sections of skeletal muscle. The demonstration of sarcoplasmic reticulum Ca-ATPase activity is complicated by the fact that capturing reagents for phosphate inhibit the enzyme. We present a minimal model for heavy-metal-phosphate precipitation reactions which gives a theoretical description of the effect of enzyme inhibition on the rate of phosphate precipitation in the section. The model indicates that the choice of capturing reagent is crucial: whether or not ATPase activity can be demonstrated depends mainly on the inhibition constant and the solubility product of the phosphate salt of the capturing reagent (but also on a fairly large number of other factors). All lanthanides tested can be used to demonstrate sarcoplasmic reticulum Ca-ATPase activity, but dysprosium results in the highest staining intensity. This suggests that dysprosium inhibits sarcoplasmic reticulum Ca-ATPase to a lesser degree than the other lanthanides and/or the solubility product of its phosphate salt is smaller. As an example, the method is used to investigate the effect of thyroid hormone on sarcoplasmic reticulum Ca-ATPase activity in individual fibres of the rat soleus muscle.
van der Laarse
W J
WJ
Laboratory for Physiology, Vrije Universiteit, Amsterdam, The Netherlands.
van Noort
P
P
Simonides
W S
WS
Diegenbach
P C
PC
Lee-de Groot
M B
MB
van Hardeveld
C
C
D000818:Animals; D000252:Calcium-Transporting ATPases / Q000032:analysis*; D004419:Dysprosium; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D005260:Female; D006651:Histocytochemistry / Q000379:methods*; D006980:Hyperthyroidism / Q000201:enzymology; D007037:Hypothyroidism / Q000201:enzymology; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000201:enzymology; D018482:Muscle, Skeletal / Q000201:enzymology; D051381:Rats; D017208:Rats, Wistar; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*; D014982:Xenopus laevis
D004791:Enzyme Inhibitors; D004419:Dysprosium; D000252:Calcium-Transporting ATPases