Adaptations to Functional Demands

Stimulation of the functions and growth of the exocrine pancreas, such as after chronic hypercholecystokininemia or partial pancreatectomy, leads to increases in the blood flow to the whole gland. Chronic pancreatitis is discussed later.

Also, the pancreatic islets increase their blood perfusion when their function is stimulated, such as initially during hyperglycemia, after partial pancreatectomy, and during pregnancy. Thus, the response of the pancreatic

EXOCRINE

Flow: 0.4-1.0 ml/min x g Pressure: 6-7 mm Hg pO2:20-25 mm Hg

Table I Effects of Different Substances on Total Pancreatic and Islet Blood Flow in Anesthetized Rats.

Substance Islet blood flow Total pancreatic blood flow

Substance Islet blood flow Total pancreatic blood flow

Nitric oxide

++

+

Endothelin

-

-

Angiotensin II

-

-

Natriuretic peptides

0 or (+)

0 or (+)

Super oxide

-

(-)

Adenosine

+

+

Indomethacin

0

0

Insulin (hypoglycaemia)

-

0

C-peptide

0

0

Glucagon

+

+

Somatostatin

-

0 or (-)

Islet amyloid polypeptide

0

-

Pancreatic polypeptide

0 or -

0 or -

Gastric inhibitory polypeptide

+**

0

Glucagon-like peptide 1

+**

0

Vasoactive intestinal polypeptide

0

++

Neuropeptide Y

0

0

Leptin

-***

0

Calcitonin gene-related peptide

-

-

Corticotropin-releasing factor

+*

+*

Cholecystokinin

-

+

Secretin

0

+

Pituitary adenylate cyclase

activating

polypeptide

0 or +

+

Substance P

-

-

Adrenaline

-

-

Metformin

+

0

Sulfonylureas

-

0

Receptors for neurotransmittors

^-adrenoceptors

-

0 or (+)

a2-adrenoceptors

+

0

M3-receptors

+

0

— denotes a decerase, + an increase, and 0 no change in blood flow. * only in the tail of the pancreas. ** only in hyperglycemic animals. *** in obese mice.

— denotes a decerase, + an increase, and 0 no change in blood flow. * only in the tail of the pancreas. ** only in hyperglycemic animals. *** in obese mice.

compartments to changes in functional demands is similar to those of other organs.

After transplantation of the whole pancreatic gland an increase in blood perfusion is consistently seen. This is likely to reflect the functional denervation of the pancreas, and especially so the lack of sympathetic nerves. Implantation of isolated islets, on the other hand, is usually associated with a decreased blood perfusion. The islets are usually transplanted into the liver and depend on stimulation of revascularization and reinnervation for their survival. There is substantial evidence for a vascular dysfunction and lack of sufficient revascularization of transplanted islets. The reader is referred to a recent review for details [11].

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