Response to creatine kinase and pressor response to orthostatic tolerance.

We thank Karamat et al1 for their comments on our recent article about sympathetic neural and pressor responses to orthostasis in elderly blacks.2 It is an interesting hypothesis that racial differences in creatine kinase (CK) levels might be one of the mechanisms for the enhanced pressor response to upright tilt in elderly blacks. However, whether CK activity measured in the blood and other tissue/organs3 accurately reflects CK concentration at the resistance vessels that provides ATP for …