Normal Renal Function: The Excretion of Water, Urea and Electrolytes Derived from Food and Drink

428 Pages·1982·9.993 MB·English

by  W. J. O’Connor MA, MD (auth.)

NORMAL RENAL FUNCTION
Normal Renal Function
The Excretion of Water, Urea and Electrolytes
Derived From Food and Drink
W.J. O'CONNOR, MA, MD
Honorary Lecturer (formerly Reader) in Physiology,
University of Leeds
CROOM HELM
London & Canberra
© 1982 W.J. O'Connor
Croom Helm Ltd, 2-10 St John's Road, London SWll
Softcover reprint of the hardcover 1s t edition 1982
British Library Cataloguing in Publication Data
O'Connor, W.J.
Normal renal function.
1. Kidneys
I. Title
612'.463 QP249
ISBN-13: 978-1-4684-1486-8 e-ISBN-13: 978-1-4684-1484-4
001: 10.1007/978-1-4684-1484-4
CONTENTS
Preface vii
1. Introduction
Section I ACUTE EXPERIMENTS ON NORMAL RENAL FUNCTION
2. Glomerular filtration rate 13
3. Renal nerves as an agent acting on the kidneys 47
4. Excretion of urea 55
5. Excretion of sulphate 77
6. Excretion of phosphate 87
7. Excretion of potassium 97
8. Excretion of sodium 111
9. Excretion of chloride and bicarbonate:
ammonium in urine 145
10. The antidiuretic action of vasopressin 163
11. Release of antidiuretic hormone from the
neurohypophysis 179
12. Acute experiments on the volume of the urine 209
13. Acute experiments on drinking by dogs 229
Section II BALANCE EXPERIMENTS
14. Intake of amino-N and excretion of urea 249
15. Intake of sulphur and excretion of sulphate 265
16. Intake of phosphorus and excretion of phosphate 273
17. Intake and excretion of potassium 283
18. Sodium balance 299
19. Intake and excretion of chloride 329
20. Anion-cation excretion: acid-base balance 335
21. Water balance 349
22. Experimental diabetes insipidus 375
References 387
Index 421
v
PREFACE
This book has developed from an earlier monograph,
'Renal Function' (1962; London, Edward Arnold). It
retains the general purpose of that book in relating
the composition of the blood to the volume and com
position of the urine of animals, including the new
data of the intervening 20 years. As indicated by
its title, this new book also has the particular
purpose of studying the urine of animals in a normal
environment and eating food usual to the species.
Renal physiology illustrates a dilemma which
arises also in other fields. Advanced technology,
harnessed by accumulated experimental skill, now
allows detailed investigation of basal processes.
Micropuncture experiments have greatly advanced our
understanding of the processes of glomerular fil
tration and tubular reabsorption and have contribut
ed to the wider discussion of the physicochemical
nature of the movement of water and ions across cell
surfaces. But experiments at microscopic or cell
ular level demand experimental conditions in which
the systems are abstracted from their natural en
vironment, either as isolated perfused preparations
or with the anaesthetised animal merely providing
support for a tissue left in situ. The arguments
from such experiments, important though they are
towards understanding the basal processes, readily
become remote from the reality of the normal animal.
If Physiology is to retain effective relationship
with the practical worlds of medicine, animal hus
bandry, nutrition, etc., there must be research on
normal animals, providing quantitative data which on
the one hand contribute to practical problems and on
the other hand pose questions for detailed investi
gation by specialists. Without experiments on nor
mal animals, Physiology will be accused of living in
an academic ivory tower and will lose its proper
status as a central biological discipline. Renal
physiology can deal with this double outlook because
methods are available for both types of experiment.
This book deals with normal renal function. The
experiments reviewed in detail are those on consci
ous animals, usually dogs, man and ruminants, where
vii
Preface
test doses have been such as to keep the composition
of plasma and urine close to the ranges of normal
life. In the published literature, one finds very
little direct investigation of normal renal functi
on. Both the specialist renal physiology and the
general reader will find here quantitative descript
ion of facts of normal renal physiology not commonly
cited and not compactly available elsewhere. These
experimental facts must endure, however interpreta
tions may change.
On the other hand since 1962 the vast mass of
work in renal physiology has been on anaesthetised
animals, especially rats using methods of micro
puncture to investigate the basal processes. There
have been many reviews and texts by those engaged in
such detailed investigations, reflecting outlooks
derived from their type of work. In this book, dis
cussion of intrarenal mechanisms is included with
the limited purpose of enquiring which of proposed
mechanisms best explain the facts of normal renal
function. Work on animals under "abnormal" condi
tions is not presehted in detail but there is ref
erence to reviews sufficient to lead into the speci
alist literature of each topic.
Because the earlier book revealed the poverty of
existing information about normal renal function, a
purpose of subsequent experimental work in this dep
artment has been to provide precise data about the
normal intake and excretion of Na, Cl, HC03, water,
urea, S04' P04 and K. This work on dogs is the ex
perimental background of the book. I gratefully
acknowledge the companionship and hard work of my
colleagues, the late D.L. Matthews, D.J. Potts,
R.A. Summerill, P. Golob and C. Baylis. I remember
also with pleasure the friendship and competent
technical assistance of J. Brook, Mrs. C. Twitchett,
Mrs. S. Snack and Mrs. V. Blakeley.
In the preparation of the book, I have been
helped by present members of the Department of
Physiology, University of Leeds. D.J. Potts, R.A.
Summerill and K.E. Lee have read all or part of the
manuscripts, corrected errors and without prejudice
to their own opinions, discussed mine. Mr. D.
Johanson provided photographic assistance in pre
paring the figures. Mrs. J. Hill, after typing ear
lier versions, prepared this final copy. I partic
ularly thank her; the book supplies its own tribute
to her professional skill.
viii
Chapter 1
INTRODUCTION
THE l'1AJOR URINARY SUBSTANCES AND THEIR ORIGINS
EXPERIMENTAL EVIDENCE
Balance experiments
Acute experiments showing solute excretion after a single ueal
Acute experiments in which the urinary solute is ingested
AGENTS WHICH ACT DI~ECTLY ON THE KIDNEYS
THE MAJOR URINARY SUBSTANCES AND THEIR ORIGINS
The function of the kidneys is to excrete and
normal function is defined in Table 1 by the quan
tities of the major urinary substances excreted
daily by man, dog and sheep eating normal food.
Substances excreted in considerable amounts and
dealt with in this book are water, urea, Na, K, Cl,
inorganic P04, inorganic S04. Other substances are
excreted in smaller amounts, too small to affect the
general picture of renal function.
Intake of these substances is in food and
drink. Table 2, extracted from the food tables of
McCance and Widdowson (Paul and Southgate, 1978)
gives the composition of typical items of food. Of
the food constituents, carbohydrates and fat are
normally oxidised to C02 and water and provide no
end products requiring renal excretion. Protein
metabolised in the body produces urea; in a state
of balance intake of N, nearly all as amino N in
protein, must be equalled by excretion of N, mostly
as urea in urine. Similarly organic compounds in
food, particularly protein, containing Sand Pare
oxidised to give inorganic S04 and in metabolism
1
Introduction
Table 1. Daily urine of animals eating normal food.
Man1 Dog 2 Sheep 3
70 kg 15 kg 60 kg
Volume litre/day 1.2 0.2 1.2
Urea mmol/day 400 250 200
K mmol/day 80 25 400
Inorganic P04 mmol/day 50 12 7
Inorganic S04 mmol/day 20 8 9
Na mmol/day 100 10 5
Cl mmol/day 120 12 200
NH4 mmol/day 40 15 10
References:- 1. As generally stated in text books. 2. Data
of Potts (1971) and Golob (1974). 3. Altman
and Dittmar (1974); Dewhurst, Harrison and
Keynes (1968).
release inorganic P04, both excreted in the urine.
K is closely associated with protein or carbo
hydrate in the food and is freed by their cata
bolism. The metabolic processes take place in gut,
liver, muscle, etc. and the formed urinary sub
stances are carried to the kidneys in the blood;
with the exception of NH4 none of the urinary
solutes is produced in the kidneys.
The intake of protein N, P, S, K is an auto
matic consequence of eating. The carnivorous
animal will have intakes of N, P, S, K in pro
portions like those in meat at the top of Table 2;
at the other extreme the herbivorous animals will
have intakes like those in vegetables and fruit
shown in the middle of the table. Urea, K, in
organic S04 and P04 are not normally added to food;
their intake is solely determined by what the animal
eats. Control of food intake is a much discussed
topic but is not specifically concerned with the
intake of N, P, S, and K. Extrarenal excretion of
these substances is small. Balance is achieved by
urinary excretion of each substance to match its
intake in food, less extrarenal losses.
The type of food determines certain character
istics of the urine. The dog eating meat has a high
protein intake and urea is some 70% of the total
solutes in urine (Table 1, column 2). Also meat
provides more inorganic anion (Cl- + S04-- + HP04--)
than cations (K+ + Na+) and the urine is acid with
H+ and NH4+ as balancing cation. At the other
extreme, sheep eating fodder of low protein content
2
Introduction
Table 2. Composition of foods (Paul and Southgate, 1978).
g/100 g mmol/100 g
P s K Na Cl
Natural foods
Lean raw meat 72 6 0 117 6.2 6.4 9.0 3.4 2.0
Raw fish 81 o 100 5.6 6.9 7.7 4.6 4.1
Milk 87 4 4.7 20 3.1 0.9 3.6 2.2 2.8
Eggs 75 11 0 70 7.1 5.6 3.6 6.1 4.5
Grains 13 80 50 3.5 3.0 3.0 0.2 1.2
(rice,
wheat flour)
Raw potatoes 76 o 21 12 1.3 1.1 14.6 0.3 2.2
Raw cabbage 90 o 4 11 1.1 2.5 7.2 0.3 0.6
Raw peas 79 o 10 33 3.2 1.6 8.7 01.0
Raw apple 85 o 12 2 0.2 0.2 3.1 0.1 0.1
Orange 86 o 8 4 0.7 0.3 5.1 0.1 0.1
Proces sec: foods
Lean bacon 67 7.4 o 115 5.8 6.5 9.0 81 79
Cheddar cheese 37 33 o 145 16.8 7.2 3.1 26 30
Butter (salted) 15 82 o 2 0.6 0.3 0.4 38 38
Bread 40 2 45 50 6.1 2.6 5.0 24 24
* In work on nitrogen balance in the past, intake and
excretion has been stated as g or mg N, the measurements
having been total N by a Kjeldahl method. N in food is
mostly as amino N of protein; about 80% of N in urine is
urea. Renal physiologists measure urea by specific methods
and state their results in mmol of urea. In this table and
throughout this book, determinations of total N have been
stated as mmol N2 = total N in mg 28; this allows
immediate comparison with urea in urine. The conventional
figure that protein (g) = 6.25 x N in g becomes 0.175 x N2
in mmo1. No such difficulties arise ~lhen S.l. units are used
for P, S, K, Na, Cl; here any values given as mg are divided
by 31, 32, 39, 23, 35.5 to give mmol.
3