The influence of sex and antenatal betamethasone exposure on vasoconstrictors and the preterm microvasculature
OBJECTIVE: Dysregulated vascular resistance contributes to hypotension following preterm birth with sex-specific differences in microvascular function conferring a male disadvantage. We hypothesized that glucocorticoid mediated, sex-specific differences in the endogenous catecholamine norepinephrine and endothelially derived endothelin-1 (ET-1) contribute to microvascular dysfunction in preterm neonates in the immediate newborn period. METHODS: Umbilical and plasma ET-1 and normetanephrine, in 24 h urine samples, were determined at 24, 72, and 120 h of age in 24-34 week infants (n = 60). Microvascular blood flow was determined by laser Doppler flowmetry. RESULTS: In infants born within 72 h of antenatal glucocorticoid exposure, normetanephrine was higher in females than males (p = 0.048). Normetanephrine was inversely correlated with both microvascular blood flow at 24 h (p = 0.025) and CRIB II (p = 0.001). While umbilical arterial ET-1 was higher in females delivered (p = 0.006), plasma ET-1 did not correlate with microvascular blood flow or illness severity. Only sex and normetanephrine contributed significantly to both microvascular blood flow and endothelium dependant vasodilatation. CONCLUSIONS: These data support glucocorticoid mediated, sex-specific differences in mediators of vascular tone that may contribute to the impaired mechanisms compromising successful hemodynamic adaption to neonatal life and resulting in excess male morbidity and mortality.