This study will investigating the effects of glucagon on renal blood flow in humans using MRI technology. Glucagon, a hormone produced by the pancreas, plays a key role in regulating blood sugar levels. It has been shown to affect renal function, including electrolyte balance and blood flow, especially in conditions like type 2 diabetes where abnormal glucagon levels are common. The study aims to understand how glucagon affects regional blood flow in the kidneys, specifically the cortex and medulla, and whether these effects are mediated by glucagon receptors.

The study will be conducted on 10 healthy male participants aged 20-60 years. It involves three test days where participants will receive either glucagon, glucagon with a GLP-1 receptor antagonist, or placebo. Blood flow, glomerular filtration rate, and other renal functions will be measured using MRI. The study seeks to clarify whether glucagon's effects on the kidneys are linked to changes in regional blood flow and to determine if these effects are mediated solely by glucagon receptors.

Inclusion Criteria:

• Normal health confirmed through; Interview and Medical examination
• Normal values with respect to blood concentrations of fasting plasma glucose, fasting plasma total cholesterol, fasting triglycerides, HDL, LDL, creatinine, liver function tests, and electrolytes
• Informed consent

Exclusion Criteria:

• Immunosuppressive treatment in the previous 12 months
• Alcohol abuse
• Medical treatment with oral glucocorticoids, dipeptidyl peptidase-4 (DPP-4) inhibitors, or GLP-1 receptor agonists, which, in the opinion of the principal investigator, may interfere with glucose metabolism
• Use of lithium
• Medical treatment that affects insulin secretion or the renin-angiotensin-aldosterone system
• Liver disease (ALT > 2x normal value)
• Renal impairment (serum creatinine > 130 µM and/or albuminuria)
• Individuals with severe claustrophobia
• Individuals with MR-incompatible foreign bodies
• Individuals with hypertension