How and why does race and gender affect risk of hypertension?

Is it somehow related to the presence of melanin?

As stated below:

Risk factors for hypertension include:

* age over 60
* male sex
* race (The African-American community has a higher incidence of hypertension.)
* heredity

* salt sensitivity
* obesity
* inactive lifestyle
* heavy alcohol consumption
* use of oral contraceptives

from: http://www.answers.com/hypertension?cat=health

Please reply if you know the answer, thank you! I am interested to find out.