In patients with autonomic dysfunction water drinking elicits a pressor response mediated by sympathetic activation. If any, in healthy subjects there is only a slight increase in blood pressure. However, the sympathetic activation is observable by resting energy expenditure increases greater than 20%.

The investigators believe that the response to water may be mediated through sympathetic activation elicited by osmosensitve spinal afferents in the liver. Therefore, the investigators want to test water in liver transplant patients who have a denervated liver. Kidney transplant patients serve as control subjects. The investigators hypothesize that the increase in norepinephrine after water drinking is blunted in liver transplant recipients.

Inclusion Criteria:

• 3 to 24 month past liver or kidney transplantation
• age 18 to 60
• written informed consent
• ability to understand the oral and written information

Exclusion Criteria:

• pregnancy or lactation
• transplantation of another organ
• chronic heart or vascular disease
• known alcohol or drug abuse
• psychiatric diseases (e.g. chronic depression, schizophrenia, drug addiction)