Table 1.

Influence of sphingolipids and N-SMase on cytosolic free [Ca²⁺]_i and [Mg²⁺]_i in single primary cultured resting rat aortic smooth muscle cells ascertained at 20 min of incubation

Sphingolipids	[Ca2+]i, nM	[Mg2+]i, μM
Control-placebo	90.7 ± 7.3	530 ± 60.1
C2-ceramide (10−5 M)	89.9 ± 6.3	713 ± 72.3**
C8-ceramide (10−5 M)	93.1 ± 7.9	730 ± 55.3**
C16-ceramide (10−5 M)	90.5 ± 6.7	829 ± 68.5**
C8-Ceramide 1-phosphate (10−5 M)	85.6 ± 8.2	551 ± 49.9
N-SMase (0.1 U/ml)	97.3 ± 6.8	723 ± 60.3**
Sphingosine (10−5 M)	170 ± 8.1**	776 ± 87.6**

All values are means ± SE of at least 35-40 cells each. N-SMase, neutral sphingomyelinase; [Ca²⁺]_i, cytosolic free Ca²⁺; [Mg²⁺]_i, cytosolic free Mg²⁺. The cover slips containing the fura 2-loaded or mag-fura 2-loaded cells were affixed to holders that were placed on the temperature-controlled stage of the fluorescence microscope. Sphingolipids (i.e., C₂-, C₈-, and C₁₆-ceramide, C₈-ceramide 1-phosphate, sphingosine, and negative analog controls) and N-SMase were incubated with primary cultured VSM cells for 20 min in 37°C. Measurements for [Ca²⁺]_i and [Mg²⁺]_i were undertaken at 20 min after exposure of these cultured cells to sphingolipids and N-SMase. Significantly different from controls (** P < 0.01, paired t-test).