AGGREGATIONto aid COAGULATION(BLOODclotting).
Other prostaglandins facilitate calcium transport to
and from cells, the onset and progression of labor
during CHILDBIRTH, and the functions of other hor-
mones. Prostaglandins are also responsible for dis-
comforts related to their release, such as after
injury when inflammation results or when men-
strual cramps (DYSMENORRHEA) occur.
Prostaglandin activity is autocrine (affects only
cells that secrete it) or paracrine (affects cells
within immediate proximity of the secreting cells).
Prostaglandin activity is also intense but short
lived, though the symptoms of the resulting
inflammation continue for some time after
prostaglandin release stops. Mast cells are the
main source of prostaglandin synthesis and secre-
tion. Epithelial cells (surface cells of the SKINand
mucous membranes) and platelets also produce as
well as respond to prostaglandins.
PROSTAGLANDINS AND THE PROSTATE GLAND
The researchers who discovered prostaglandins
in the 1930s isolated the first member of this bio-
chemical family from SEMEN—the secretions of
the PROSTATE GLAND. They named it for this con-
nection. Over the following decades further
research identified a number of prostaglandins
and determined that nearly every cell in the
body contains some form of prostaglandin.
Aspirin was the first DRUGto block the synthesis
of prostaglandins.The enzymes cyclooxygenase 1 (COX-1) and
COX-2 facilitate the synthesis of prostaglandins
from arachidonic acid, an essential fatty acid (a
fatty acid the body requires for health but cannot
synthesize from other substances so must obtain
from dietary sources) found in red meats and
peanuts. Arachidonic acid is also the foundation
for LEUKOTRIENES, other biochemicals also involved
in the inflammatory response. The enzyme lipoxy-
genase facilitates the conversion of arachidonic
acid to leukotrienes. COX-1 is primarily in the
STOMACH, KIDNEYS, and walls of the blood vessels; it
maintains the prostaglandins necessary for the
body’s normal functioning. COX-2 is present in
the tissues and becomes active during an inflam-
matory response.
NONSTEROIDAL ANTI-INFLAMMATORY DRUGS(NSAIDS),
including aspirin, block the action of COX, pre-
venting prostaglandin production. This action
provides pain relief, reduces fever, and mitigates
the swelling associated with inflammation.
Though much therapeutic focus is on blocking
prostaglandin production, there are numerous
therapeutic applications for synthetic
prostaglandins. Therapeutic administration of syn-
thetic prosta-glandin E 1 (PGE 1 ) maintains a patent
ductus arteriosus in infants born with serious con-
genital heart defects. Prostaglandin E 2 (PGE 2 ) and
prostaglandin F 2 (PGF 2 ) cause the UTERUSto con-
tract, either initiating or strengthening labor.
See also CONGENITAL HEART DISEASE; CRAMP; HOR-
MONE; IMMUNE RESPONSE; IMMUNOGLOBULIN; MAST
CELL; PLATELET.psychoneuroimmunology The interrelationships
between emotions, neurologic function, and the
IMMUNE SYSTEM. In the 1970s researchers discov-
ered receptors for neuropeptides on cells through-
out the body, including the immune system. The
BRAIN produces neuropeptides, protein-based
structures that convey biochemical messages
related to cognition (thought and logic) and emo-
tion. Neuropeptides include endorphins and
enkephalins, substances connected to perceptions
of SATIETYand pleasure.
Though researchers do not yet understand how
neuropeptides affect IMMUNE RESPONSE, they do
know emotional stress affects physical health.
They also know that the immune system affects
neurologic functions, which is one reason people
feel irritable and cranky when they are sick. It
appears that the primary messengers for immune-
to-neural communication are the CYTOKINES
immune cells produce during the immune
response, notably INTERLEUKINS, which are capable
of activating NERVEimpulses that convey signals to
the brain. Researchers continue to explore ways to
use these connections for health, HEALING, and dis-
ease prevention.
See also MIND–BODY CONNECTION.reticuloendothelial system See MONONUCLEAR
PHAGOCYTE SYSTEM.290 The Immune System and Allergies