. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 70 J. F. S1EBENALLER AND T F. MURRAY. 120 Time (min) Figure 5. Time course of the adcnylyl cyclase reaction at 5°C in brain membranes from Anlimora roMruui. Open circles: basal adenylyl cyclase activity. Filled circles: forskolin ( ) stimulated activity. Reaction mixture contained 50 m,U HHPES, pH , at 5°C, 4 magnesium acetate, 50 2-deoxy ATP. 100 »M cAMP. 200 ,,A/ pa- paverine, mgcreatinephosphate, 2 mgcreatinephosphokinase, 100 m-A/NaCl, 10 jiA/GTP, and units/ml adenosinedeaminase. branes are shown
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 70 J. F. S1EBENALLER AND T F. MURRAY. 120 Time (min) Figure 5. Time course of the adcnylyl cyclase reaction at 5°C in brain membranes from Anlimora roMruui. Open circles: basal adenylyl cyclase activity. Filled circles: forskolin ( ) stimulated activity. Reaction mixture contained 50 m,U HHPES, pH , at 5°C, 4 magnesium acetate, 50 2-deoxy ATP. 100 »M cAMP. 200 ,,A/ pa- paverine, mgcreatinephosphate, 2 mgcreatinephosphokinase, 100 m-A/NaCl, 10 jiA/GTP, and units/ml adenosinedeaminase. branes are shown in Figure 5. At 5°C, both the basal and forskolin-stimulated rates were linear for at least 120 min. An incubation time of 120 min was used for all sub- sequent experiments. The inhibition of basal adenylyl cyclase activity by Nh- cyclopentyladenosine (CPA) was used as a biochemical measure of the extent of coupling of A, receptors to ad- enylyl cyclase via a guanine nucleotide regulatory pro- tein. CPA is a highly selective A, adenosine receptor ago- nist and was used to eliminate potential interactions with the A 2 adenosine receptor (Bruns el ai. 1986; Williams ft ai, 1986) or with the P-site on the catalytic subunit of adenylyl cyclase (Londos el ai. 1983; Blair et ai. 1989; Johnson et ai. 1989). The dependence of CPA-induced inhibition of adenylyl cyclase activity on GTP concen- tration is depicted in Figure 6. Basal adenylyl cyclase ac- tivity in the absence and presence of 100 ^A/ CPA is shown. CPA had little effect on adenylyl cyclase activity in the absence of added GTP; however, at GTP concen- trations of 1 to 100 nM. the Ai selective agonist inhibited activity. A representative concentration response curve in Figure 7 depicts the inhibition of basal adenylyl cy- clase activity in A. rostrata brain membranes by various concentrations of CPA. The IC?I) value for inhibition of adenylyl cyclase was ± fiM. The maximal inhi- bition of basal activity by CPA r
Size: 2093px × 1194px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
