LECTURE 8 - OUTLINE Endocrine Systems II Introduction
Pituitary Gland




1. Nomenclature & anatomy 2. Cytology & hormones (I) lactotropes




(II) thyrotropes (III) corticotropes

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. - inhibition of PRL release using bromocriptine implants - reduced aggression - increased ring circling - reduced egg fanning (fungus!)

Bluegill (Lepomis sp.) BIOL 4340 – Lecture 8 - 2

1

Pituitary Gland (hypophysis) 2. Cytology and hormones (II) thyrotropes – rostral pars distalis, thyrotropin (TSH) - controls thyroid gland function, thyroid hormone levels thyroxine (T4)

3,5,3”-triiodothyronine (T3)

thyrotropes lactotropes

corticotropes

gonadotropes

somatotropes 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

2

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 - thyroid hormones regulate basal metabolic rate

Migration of fishes (fasting)

n in

10

wn

8

ing

pr e-s pa w

pa

6

po sts

- active thyroid gland at the beginning of breeding migration

Thyroxine (ng/ml)

- increased thyroid gland activity in migrating Atlantic salmon

g

12

4 2

Lampetra fluviatilis

SW

FW 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

Hibernation - Black bear (Ursus americanus) - metabolic rate very low - hibernation-induced hypothyroidism - reduced TSH & thyroid hormones

BIOL 4340 – Lecture 8 - 6

3

Pituitary Gland (hypophysis) African lungfish estivation - 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

BIOL 4340 – Lecture 8 - 7

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

4

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

Thyroxine (ng/g body weight)

Flounder metamorphosis 14

- stage 0-1, Premetamorphosis 10

- stage 2, Metamorphosis (early) - stage 3, Metamorphosis (late)

6

- stage 3.5, Juvenile

2 0-1 3 3.5 2 Developmental Stage

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

Thyroxine (ng/g body weight)

Flounder metamorphosis

Altering Thyroid Status

14

- U: untreated

10

- T4: 100 ppb T4 in water 6

- TU: 30 ppm Thiourea in water (thiourea inhibits T4 synthesis)

2 U

T4 Treatment

TU BIOL 4340 – Lecture 8 - 10

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 Flounder metamorphosis - stage 2, Metamorphosis (early) - stage 3, Metamorphosis (late) - stage 3.5, Juvenile

- experiment started 27 dph

: Control

(36 dph)

: 100 ppb T4 (30 dph)

Stage of metamorphosis

- stage 0-1, Premetamorphosis

3.5

: 30 ppm Thiourea (43 dph)

3 2.5 2 1.5 1 0.5 0 30

Age (dph)

60 BIOL 4340 – Lecture 8 - 11

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

Pituitary Gland (hypophysis) 2. Cytology and hormones (III) corticotropes – rostral pars distalis, corticotropin (ACTH) - stimulates steroid biosynthesis & secretion, interrenals - hypothalamic-pituitary-interrenal (HPI) axis head

trunk

pcv

interrenal tissue pcv – postcardinal vein BIOL 4340 – Lecture 8 - 12

6

Pituitary Gland (hypophysis) 2. Cytology and hormones (III) corticotropes – rostral pars distalis, corticotropin (ACTH) - ACTH dominates control of corticosteroid secretion

cortisol release (ng/h/kg)

180

Mammalia

ACTH

- corticosterone - cortisol - aldosterone

120

glucocorticoids mineralocorticoids

Cyclostomes - cortisol, corticosterone [tentative] 60

0 0

70

140

210 BIOL 4340 – Lecture 8 - 13

time (min)

Pituitary Gland (hypophysis) 2. Cytology and hormones (III) corticotropes – rostral pars distalis, corticotropin (ACTH) - ACTH dominates control of corticosteroid secretion

cortisol release (ng/h/kg)

180

Chondrichthyes

ACTH

Elasmobranchii - 1α-hydroxycorticosterone Holocephali - cortisol

120

Actinopterygii - cortisol

60

Sarcoptyregii (lungfishes) 0 0

70

140

time (min)

210

- cortisol - aldosterone BIOL 4340 – Lecture 8 - 14

7