TABLE 4.

In vitro metabolism of testosterone by LNG microsomes from WT and Cyp2a5-null mice

Rates of formation of 15α-OH-T, 15β-OH-T, 2β-OH-T, and 16α-OH-T, as well as the rates of disappearance of testosterone, in microsomal incubations, were determined. Reaction mixtures contained 50 mM potassium phosphate buffer, pH 7.4, 10 μM (for metabolite formation) or 10 nM (for substrate disappearance) testosterone, 1.0 mM ascorbic acid, 0.5 mg/ml LNG microsomal protein from 2-month-old male mice, and 1.0 mM NADPH. The values presented are means ± S.D. (n = 3).

Strain	Rates of Product Formation				Rates of Testosterone Disappearance
	15α-OH-T	15β-OH-T	2β-OH-T	16α-OH-T
	pmol · min−1 · mg protein−1
WT B6	106 ± 19	7.8 ± 1.6	8.8 ± 2.5	12.0 ± 2.0	0.7 ± 0.03
Cyp2a5-null	0.3 ± 0.1a	< 0.04a	< 0.4a	11.7 ± 1.5	0.3 ± 0.02a

OH-T, hydroxytestosterone.

^aP < 0.01 compared with the corresponding value of WT mice.