1

LECTURE 8 - OUTLINE

Endocrine Systems II

1. Nomenclature & anatomy

2. Cytology & hormones

(I) lactotropes

Introduction

Pituitary Gland

(II) thyrotropes

(III) corticotropes

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BIOL 4340 – Lecture 8 - 1

Pituitary Gland (hypophysis)

2. Cytology and hormones

(I) lactotropes – rostral pars distalis, prolactin (PRL)

- osmoregulation

- reproduction (lactogenesis)

- may play a role in parental care

e.g. trophic provisioning

- increased mucus production

in Symphysodon spp.

BIOL 4340 – Lecture 8 - 2

Bluegill (Lepomis sp.)

- inhibition of PRL release

using bromocriptine implants

- reduced aggression

- increased ring circling

- reduced egg fanning (fungus!)

2

Pituitary Gland (hypophysis)

2. Cytology and hormones

(II) thyrotropes – rostral pars distalis, thyrotropin (TSH)

lactotropes

thyrotropes

corticotropes

gonadotropes

somatotropes

- controls thyroid gland function, thyroid hormone levels

thyroxine (T4) 3,5,3”-triiodothyronine (T3)

BIOL 4340 – Lecture 8 - 3

Pituitary Gland (hypophysis)

2. Cytology and hormones

(II) thyrotropes – rostral pars distalis, thyrotropin (TSH)

- controls thyroid gland function, thyroid hormone levels

- thyroid hormones influence most bodily functions

1. Growth 2. Differentiation 3. Metamorphosis

4. Reproduction 5. Hibernation 6. Thermogenesis

BIOL 4340 – Lecture 8 - 4

3

Pituitary Gland (hypophysis)

2. Cytology and hormones

(II) thyrotropes – rostral pars distalis, thyrotropin (TSH)

- controls thyroid gland function, thyroid hormone levels

- thyroid hormones regulate basal metabolic rate

- thyroid hormones influence most bodily functions

Migration of fishes (fasting)

- increased thyroid gland activity in

migrating Atlantic salmon

Lampetra fluviatilis

- active thyroid gland at the beginning

of breeding migration

SW FW

Th

yro

xin

e(n

g/m

l)

12

8

6

4

2

10

pre

-spaw

nin

g

post

-spaw

nin

g

BIOL 4340 – Lecture 8 - 5

Pituitary Gland (hypophysis)

2. Cytology and hormones

(II) thyrotropes – rostral pars distalis, thyrotropin (TSH)

- controls thyroid gland function, thyroid hormone levels

- thyroid hormones influence most bodily functions

1. Growth 2. Differentiation 3. Metamorphosis

4. Reproduction 5. Hibernation 6. Thermogenesis

- Black bear (Ursus americanus)

- hibernation-induced hypothyroidism

- reduced TSH & thyroid hormones

- metabolic rate very low

Hibernation

BIOL 4340 – Lecture 8 - 6

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Pituitary Gland (hypophysis)

African lungfish estivation

BIOL 4340 – Lecture 8 - 7

- estivation may last 2 - 3 years in African lungfish

- thyroid hormone secretions become 1/75 of normal

- pituitary TSH content similar in estivating and normal fish

- hypophysectomy had no effect on estivating fish

- intact pituitary essential for survival upon emegrence

Pituitary Gland (hypophysis)

2. Cytology and hormones

(II) thyrotropes – rostral pars distalis, thyrotropin (TSH)

- controls thyroid gland function, thyroid hormone levels

- thyroid hormones influence most bodily functions

1. Growth 2. Differentiation 3. Metamorphosis

4. Reproduction 5. Hibernation 6. Thermogenesis

BIOL 4340 – Lecture 8 - 8

5

Pituitary Gland (hypophysis)

2. Cytology and hormones

(II) thyrotropes – rostral pars distalis, thyrotropin (TSH)

- controls thyroid gland function, thyroid hormone levels

- thyroid hormones influence most bodily functions

Th

yro

xin

e(n

g/g

bo

dy w

eig

ht)

14

10

6

2

0-1 2 3 3.5

Developmental Stage

Flounder metamorphosis

- stage 3.5, Juvenile

- stage 3, Metamorphosis (late)

- stage 2, Metamorphosis (early)

- stage 0-1, Premetamorphosis

BIOL 4340 – Lecture 8 - 9

Pituitary Gland (hypophysis)

2. Cytology and hormones

(II) thyrotropes – rostral pars distalis, thyrotropin (TSH)

- controls thyroid gland function, thyroid hormone levels

- thyroid hormones influence most bodily functions

Th

yro

xin

e(n

g/g

bo

dy w

eig

ht)

14

10

6

2

U T4 TU

Treatment

Flounder metamorphosis

- TU: 30 ppm Thiourea in water

- T4: 100 ppb T4 in water

- U: untreated

Altering Thyroid Status

(thiourea inhibits T4 synthesis)

BIOL 4340 – Lecture 8 - 10

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Pituitary Gland (hypophysis)

2. Cytology and hormones

(II) thyrotropes – rostral pars distalis, thyrotropin (TSH)

- controls thyroid gland function, thyroid hormone levels

- thyroid hormones influence most bodily functions

- stage 0-1, Premetamorphosis

- stage 2, Metamorphosis (early)

- stage 3, Metamorphosis (late)

- stage 3.5, Juvenile

Flounder metamorphosis

: Control

: 100 ppb T4

: 30 ppm Thiourea

3.5

3

1.5

2.5

2

1

0.5

0

Age (dph)

Sta

ge o

f m

eta

mo

rph

osis

6030

Schreiber & Specker 1998. Gen Comp Endocrinol 111: 156-166

- experiment started 27 dph

(36 dph)

(30 dph)

(43 dph)

BIOL 4340 – Lecture 8 - 11

Pituitary Gland (hypophysis)

2. Cytology and hormones

(III) corticotropes – rostral pars distalis, corticotropin (ACTH)

head trunk

pcv

pcv – postcardinal vein

interrenal tissue

BIOL 4340 – Lecture 8 - 12

- hypothalamic-pituitary-interrenal (HPI) axis

- stimulates steroid biosynthesis & secretion, interrenals

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Pituitary Gland (hypophysis)

2. Cytology and hormones

(III) corticotropes – rostral pars distalis, corticotropin (ACTH)

- ACTH dominates control of corticosteroid secretion

0

60

120

180

70 140 2100

co

rtis

ol

rele

ase (

ng

/h/k

g)

time (min)

ACTHMammalia

- corticosterone

- cortisol

- aldosterone

glucocorticoids

mineralocorticoids

BIOL 4340 – Lecture 8 - 13

Cyclostomes

- cortisol, corticosterone [tentative]

Pituitary Gland (hypophysis)

2. Cytology and hormones

(III) corticotropes – rostral pars distalis, corticotropin (ACTH)

- ACTH dominates control of corticosteroid secretion

Chondrichthyes

- 1α-hydroxycorticosterone

Elasmobranchii

- cortisol

Holocephali

Actinopterygii

- cortisol

Sarcoptyregii (lungfishes)

- cortisol- aldosterone

0

60

120

180

70 140 2100

co

rtis

ol

rele

ase (

ng

/h/k

g)

time (min)

ACTH

BIOL 4340 – Lecture 8 - 14