Tissue hormones

1
TISSUE HORMONES OR PARA HORMONES

• M.Prasad Naidu
• MSc Medical Biochemistry, Ph.D,.

2
PARA HORMONES

• Tissue hormones
• Local hormones
• Act on the tissue on which they are produced
• Short lived
• Paracrine in nature
• Eg melatonin, renal hormones, eicosanoids and
  opiate peptides

3
Melatonin

• Pineal gland or epiphysis hormone
• Tiny conical or pine-like organ
• On the dorsal side of brain in vertebrates lying
  deep in the groove b/n cerebellum and cerebral
  hemispheres
• Clock work gland
• Sphincter of thought the minds valve
• The seat of the rational soul
• A neurological transducer a system that
  converts nerve type signal into an endocrine
  signal
• Very well developed in children and shrinks after
  the 7th year and reduced to a little knot after
  puberty
• Weighs less than a button

4
structure

• Pineal secretes a hormone melatonin
• Melatonin inhibits the secretion of LH
• Serotonin is the precursor under the influence of
  2 enzymes
• N-acetyl transferase (NAT)
• Hydroxyindole-0-methyltransferase (HIOMT)
• Pineal manufactures melatonin only in the night
• It does not sit idle and converts Try into
  serotonin which accumulates and stored in
  inactive form until night
• Neurotransmitters like NEP ? NAT HIOMT
• Exposure to light slows while exposure to
  darkness stimulates the production of melatonin
• Pineal is under the control of sp.nerve cells
  found in hypothalamus called supra chiasmatic
  nuclei (SCN)
• SCN turns melatonin production on off in the
  pineal by directing the nightly increase in NAT

5
Functions

• In humans, the glands rhythm may affect the sleep
  cycle
• Melatonin makes people drowsy (sleeping aide)
• Prevents cancer
• Strengthens the immune system
• This miracle hormone keeps a person using it away
  from growing old
• Melatonin production ? age
• Regulates menstrual cycle in females
• Regulates sperm production in males

6
Renal Hormones

• Kidney secrets 2 hormones
• 1. Erythropoietin/Erythrocyte stimulating factor
  ESF
• 2. Renin
• ESF secretion is stimulated by androgens and
  cobalt
• Initially secreted as inactive protein called
  Renal Erythropoietin Factor (REF)
• REF is like an enzyme converts plasma globulin
  into active erythropoietin
• Glycoprotein 8-12 hexose 60000
• Lacks Met
• Its activity is retarded by antibiotic
  actinomycin D and also by proteolytic enzymes
• ESF stimulates Bone marrow ? no.of
  proerythroblasts ? reticulocytes (precursor of
  erythrocytes)
• Stimulates the synthesis of a very large RNA (
  150S) by bone marrow cells

7
Renin

• Catalyzes the synthesis of angiotensins
• Angiotensins ? vasoconstriction in kidneys ?
  electrolyte water retention in the body
• This system ? renin-angiotensin system
• ? renal pressure , ? plasma Na , ? angiotensins
  ? ? renin production

8
Eicosanoid hormones

• Eicosanoids
• FA derivatives
• Involved in reproductive function
• In the inflammation
• In fever pain
• In the formation of blood clots
• In the regulation of blood pressure
• In gastric acid secretion

9
Eicosanoids

• Derived from Arachidonic acid
• Also called signal molecules
• 3 types
• 1.Prostaglandins
• 2. Prostacyclins thromboxanes
• 3. Leucotrienes

10
Prostaglandins

• Von Euler 1935
• Lipid soluble acidic substances
• Semen is the richest source
• Also found in Brain, spinal cord, thymus, lungs,
  pancreas, kidneys, menstrual fluid and placenta
• Resembles prostanoic acid
• Hydroxy derivatives of poly unsaturated FAs
• Can be divided into 9 groups (A to I)
• PGE ? ether soluble , has a keto group at C9
• PGF ? phosphate buffer soluble, a OH group at C9

11
Prostaglandins

• Half life 5 mins
• Destroyed rapidly
• High turn over rate
• The most revolutionary therapeutic substances
• Affects smooth muscles and bp
• Often the activities of individual PGs oppose one
  another
• Eg PGE2 dialates blood vessels and bronchi
• PGF2a constricts

12
Functions

• Contraction and relaxation of the smooth muscles
  of the uterus especially at the time of ovulation
• This may be due to chelation of Ca
• 1ng/ml can cause contraction
• Thus it resembles oxytocin
• ? bp
• ? lipolysis in AT ? conversion of ATP to cAMP
• ? platelet aggregation
• PGs have opposite effect on EP, NEP, glucagon,
  ACTH on the release of FAs from AT
• Affects CVS (behaves both pressor and depressor
  agents)
• Appear to control the secretion of gastric HCl
• Have some beneficial effect in the control of the
  acid-induced gastric ulcers
• Effect on reproductive system- male fertility
• Low PGs in human semen is related to infertility
• Also involved in inflammatory reaction pain
• anti-inflammatory drug such as aspirin , act by
  inhibitin the synthesis of PGs

13
Thromboxanes and prostacyclins

• TXAs and PGIs are structurally related both
  arise from nascent PG
• TXA2 was first isolated from platelets
• PGI2 produced primarily in blood vessels
• TXAs and PGIs displays a critical balance
  required for the normal functioning in the body
• TXA2 is a highly effective vasoconstrictor and
  platelet aggregator
• PGI2 is a potent vasodialator and inhibitor or
  platelet aggregation

14
Functions

• PGIs inhibits platelet aggregation
• PGIs relaxes coronary arteries
• PGIs lowers BP
• TXAs stimulates platelet aggregation
• TXAs constricts coronary arteries
• TXAs raises BP

15
Leukotrienes (LTs)

• Precursor Arachidonate
• Enzyme lipoxygenase
• Cysteinyl-containing derivatives of arachidonic
  acid with a series of 3 conjugated double bonds
• Eg LTB4, LTC4, LTD4, LTE4
• Neutrophils make one class of LTs to alter
  mobility and act as chemotactic agents
• Mast cells make another class ( formerly known as
  slow-reacting substances) which are responsible
  for bronchial constriction and other anaphylactic
  allergic reactions
• Over production of LTs cause asthamatic attacks
  and also stimulates mucus secretion

16
Opiate peptides

• 3 families
• Enkephalins consist of 5-7 amino acids
• Derived from proenkephalin
• Isolated from extracts of brain pituitary and
  exhibit morphine like properties
• Dynorphins 10-17 AAs
• Derived from prodynorphin
• Endogenous compounds made in several locations
• Major locations brain, pituitary, adrenal
  medulla, and peptidergic neurons
• Endorphins 16-27 AAs
• Proopiomelanocortin (POMC)
• Isolated from extracts of brain, pituitary
  exhibit morphine like properties

17
PHEROMONES

• Social hormones
• Smell signals
• Species specific chemical substances
• 1982 survey in USA on taste smell
• Strong link b/n sex and smell
• Odour which are released from animals into the
  environment and evoke behavioural, developmental
  and reproductive responses
• Karlson Luscher

18
Pheromones

• Pheromones work on the other members of the same
  species (hormones ?)
• Pheromones are produced in glands and discharged
  externally to influence other members of the same
  species
• Well known sex attractants

19
Structure

• Chemically diverse group
• AAs, Lipids, alcohols, org.acids
• Female silk worm moth (Bombax mori) secretes a
  sex-attractant which attracts male moths
• It is a long chain alcohol ( C16H30O)
• With 2 double bonds C10 C12

20
Structure

• Insects also secrete alarm pheromones
• Many of these are hydrocarbons, oxidized
  hydrocarbons, terpenoid in nature
• Eg Tridecane, Heptan-2-one, Citronellal, a-pinene

21
Types of pheromones

• Based on their function, 2 types
• 1. Releaser pheromones stimulate specific
  patterns of behaviour
• Powerful sex-attractants, mark-territories or
  trails
• They initiate alarm reactions or bring about
  aggregation of individuals
• 2. Primer pheromones
• They trigger physiological changes in endocrine
  activity esp related to sexual maturation, growth
  or metamorphosis

22
Examples

• In the honey bee colony, the Queen bee secretes
  Queen substance which inhibits the growth of
  ovaries in the worker bees.
• The honey bee inject an alarm substance called 2-
  heptanone in the body of the victim it stings
• Synthetically produced restenol can give the
  right fragnance to make love
• Androstenone, a hormone found in perspiration
  from the armpit and genitals is found more in men
  than women
• Couplins are estrogen dependent fatty acids found
  in vaginal secretions of some women
• The testes form a steroid called priapol (
  trivial name)

23
THANK YOU