Table 2.

Inward and Outward I_NCX densities at the base and apex of adult female and male hearts

		N/P	Mean ±s.d.	Median (25–75% range)	P values
Female Base	Outward INCX	4/8	0.83 ± 0.44	0.81	†0.03
				(0.54 ÷ 1.00)	#0.009
	Inward INCX	4/12	−0.55 ± 0.36	−0.46	†<0.01
				(−0.82 ÷−0.25)	#0.33
Female Apex	Outward INCX	4/8	0.31 ± 0.32	0.26	#0.03
				(0.04 ÷ 0.58)
	Inward INCX	4/12	−0.38 ± 0.38	−0.20	#0.95
				(−0.67 ÷−0.06)
Male Base	Outward INCX	4/8	0.31 ± 0.27	0.25	†0.04
				(0.14 ÷ 0.48)
	Inward INCX	4/12	−0.64 ± 0.29	−0.63	†<0.01
				(−0.85 ÷−0.41)
Male Apex	Outward INCX	4/8	0.72 ± 0.27	0.66
				(0.52 ÷ 1.01)
	Inward INCX	4/12	−0.33 ± 0.23	−0.37
				(−0.51 ÷−0.15)

^†Base versus Apex for each heart using Wilcoxon matched pairs test;

^#Female versus Male groups using Mann–Whitney U test (unpaired).

Four groups of myocytes were investigated: female base and apex and male base and apex (N= 4 hearts of each sex). The mean inward I_NCX density (±s.d.) was calculated at three voltages (−80, −60, and −40 mV) from base myocytes of each heart and compared to measurements from apex myocytes of the same heart. Similarly, the mean outward I_NCX density (±s.d.) was calculated at two voltage values (0 and 20 mV) from base myocytes of each heart and compared to measurements from apex myocytes from the same heart. In some hearts, several myocytes (n= 1–3) were used to calculate the mean inward and outward I_NCX.