Table 1:

Intracellular free calcium levels of caudal sperm incubated under capacitating or non-capacitating conditions in the presence or absence of FK506 (20nM) were measured as described in materials and methods. The table also shows calcineurin activity of untreated sperm extracts with the addition of free calcium (found in caput sperm or non-capacitated and capacitated caudal sperm). For comparison, the values for intracellular calcium and calcineurin activity are also shown for caput sperm. Data for calcium levels and calcineurin activity are means ± SEM. *[Ca₂⁺]_i levels shown in the preceding column were used in the corresponding calcineurin activity assay medium; **20 nM FK506 was added to the calcineurin activity assay medium for this set and it should be treated as the negative control for this activity assay.

Sperm type	Incubating condition	Treatment	Measured [Ca2+] (in nM) (n=5)	Corresponding CaN activity (nmol phosphate released/hr) (n=3)*
Caput epididymal sperm	-	-	961±66	1.06±0.084
Caudal epididymal sperm	Non-capacitating	-	287±25	0.22±0.02 (p ≤0.01)
	Capacitating	1% EtOH	897±52	0.78±0.046
		20 nM FK506	826±55	**0.030±0.004 (p ≤0.01)