TABLE 3

Potencies and efficacies of FS and FS analogs on mouse heart AC and AC5 For those FS analogs not reaching saturation of the concentration-response curves, the actual stimulatory effect at a concentration of 300 μM was used for calculation of efficacy. AC activities were determined as described under Materials and Methods. Reaction mixtures contained 10 mM Mn²⁺, 40 μM ATP, [α-³²P]ATP (0.2–1.0 μCi/tube), 10 μM GTPγS, 0.4 mg/ml creatine kinase, 9 mM phosphocreatine, 100 μM cAMP, and 100 μM IBMX. EC₅₀ values and efficacies were obtained by nonlinear regression analysis and are the means ± S.D. of three to four independent experiments performed in duplicates.

Diterpene	Cardiac AC EC₅₀	Cardiac AC Efficacy	AC5 EC₅₀	AC5 Efficacy
	μM	%	μM	%
FS	3.0 ± 0.2	100	4.0 ± 0.6	100
6A7DA-FS	3.6 ± 0.5	76 ± 10	7.4 ± 2.8^b	103 ± 11^b
BODIPY-FS	1.4 ± 0.5	54 ± 6	2.3 ± 1.1^b	48 ± 2^b
7DA-FS	30.2 ± 10.2^a	83 ± 5^a	63.3 ± 10.6^b	63 ± 4^b
9d-FS	38.6 ± 19.2^a	90 ± 12^a	65.3 ± 9.0^b	79 ± 10^b
DMB-FS	17.4 ± 2.0^a	118 ± 4^a	48.0 ± 9.6^b	95 ± 1^b
1d-FS	Ineffective			Ineffective^b

↵ a Extrapolated EC₅₀ values were derived from concentration-response curves that did not reach saturation
↵ b Values were taken from Pinto et al. (2008)