Table 1.

The ability of ceramide and various analogs to permeabilize the outer membrane of isolated rat liver mitochondria and rat erythrocytes, and inhibit the enzymatic activity of cytochrome oxidase. The first compound (#1) is the natural stereoisomer.

(#) Name	Type of change	MOM Permeabilization relative to C16-ceramidea	Erythrocyte Lysis (%)a mean±S.D.	Oxidase Inhibition
(1) (2S,3R,4E) C16-ceramide	stereo-chemistry	1	<2	No
(2) (2R,3S,4E) C16-ceramide		0.16±0.04**	18 ± 0.1***	No
(3) (2S,3S,4E) C16-ceramide		0.80±0.09*	32 ± 2**	No
(4) (2S,3R,4E) C16-ceramine	amide linkage	N/D	48 ± 2***	Yes
(5) (2S,3R,4E) C16-urea-ceramide		2.29±0.07***	52 ± 2***	No
(6) (2S,3R,4E) N-methyl-C16-ceramide		0.21±0.04*	<2	No
(7) (2S,3R,4E) 1-O-methyl-C16-ceramide	hydroxyl groups	0.0***	<2	No
(8) (2S,3R,4E) 3-O-methyl-C16-ceramide		1.1±0.15	66 ± 7**	No
(9) (2S,3R) C16-dh-ceramideb	double bond	0.0****	<2	No
(10) (2S,3R,4R) C16-phytoceramide		2.3±0.5*	24 ± 1***	No
(11) (2S,3R) C16-4,5-deh-ceramideb		1.2±0.2	48 ± 2***	No
(12) (2S,3R,4E) C16-(4,5-allene)-ceramide		3.0±0.26*	69 ± 1***	No
(13) (2S,3R,15E) C16-dh*-ceramideb		3.8±0.59***	57 ± 5**	No
(14) (2S,3R,4E) C10-ceramide	acyl chains	6.6±0.26***	87 ± 0.5***	No
(15) (2S,3R,4E) 13C/C16-ceramide		6.1±0.27***	43 ± 2***	No
(16) (2S,3R,4E) C6-NBD-ceramide		N/D	13 ± 5*c	Yes
(17) (2S,3R,4E) C18:1-ceramide		N/D	42 ± 3**	Yes

^aStatistical significance was determined using the Student's t test and the P values are as follows:

^*<.05

^**<.01

^***<.001; values are given as mean ± SE of at least 3 experiments

^bdh is dihydro; deh is dehydro/triple bond.

^cThe dose of the analog was 10 times less than for the rest.

N/D: not done.